Water-dispersible and multicomponent fibers from sulfopolyesters

ABSTRACT

Disclosed are water-dispersible fibers derived from sulfopolyesters having a Tg of at least 25° C. The fibers may contain a single sulfopolyester or a blend of a sulfopolyester with a water-dispersible or water-nondispersible polymer. Also disclosed are multicomponent fibers comprising a water dispersible sulfopolyester having a Tg of at least 57° C. and a water non-dispersible polymer. The multicomponent fibers may be used to produce microdenier fibers. Fibrous articles may be produced from the water-dispersible fibers, multicomponent fibers, and microdenier fibers. The fibrous articles include water-dispersible and microdenier nonwoven webs, fabrics, and multilayered articles such as wipes, gauze, tissue, diapers, panty liners, sanitary napkins, bandages, and surgical dressings. Also disclosed is a process for water-dispersible fibers, nonwoven fabrics, and microdenier webs. The fibers and fibrous articles have further applications in flushable personal care and cleaning products, disposable protective outerwear, and laminating binders.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.10/465,698, filed Jun. 19, 2003.

FIELD OF THE INVENTION

The present invention pertains to water-dispersible fibers and fibrousarticles comprising a sulfopolyester. The invention further pertains tomulticomponent fibers comprising a sulfopolyester and the microdenierfibers and fibrous articles prepared therefrom. The invention alsopertains to processes for water-dispersible, multicomponent, andmicrodenier fibers and to nonwoven fabrics prepared therefrom. Thefibers and fibrous articles have applications in flushable personal careproducts and medical products.

BACKGROUND OF THE INVENTION

Fibers, melt blown webs and other melt spun fibrous articles have beenmade from thermoplastic polymers, such as poly(propylene), polyamides,and polyesters. One common application of these fibers and fibrousarticles are nonwoven fabrics and, in particular, in personal careproducts such as wipes, feminine hygiene products, baby diapers, adultincontinence briefs, hospital/surgical and other medical disposables,protective fabrics and layers, geotextiles, industrial wipes, and filtermedia. Unfortunately, the personal care products mades from conventionalthermoplastic polymers are difficult to dispose of and are usuallyplaced in landfills. One promising alternative method of disposal is tomake these products or their components “flushable”, i.e., compatiblewith public sewerage systems. The use of water-dispersible orwater-soluble materials also improves recyclability and reclamation ofpersonal care products. The various thermoplastic polymers now used inpersonal care products are not inherently water-dispersible or solubleand, hence, do not produce articles that readily disintegrate and can bedisposed of in a sewerage system or recycled easily.

The desirability of flushable personal care products has resulted in aneed for fibers, nonwovens, and other fibrous articles with variousdegrees of water-responsivity. Various approaches to addressing theseneeds have been described, for example, in U.S. Pat. Nos. 6,548,592;6,552,162; 5,281,306; 5,292,581; 5,935,880; and 5,509,913; U.S. patentapplication Ser. Nos. 09/775,312; and 09/752,017; and PCT InternationalPublication No. WO 01/66666 A2. These approaches, however, suffer from anumber of disadvantages and do not provide a fibrous article, such as afiber or nonwoven fabric, that possesses a satisfactory balance ofperformance properties, such as tensile strength, absorptivity,flexibility, and fabric integrity under both wet or dry conditions.

For example, typical nonwoven technology is based on themultidirectional deposition of fibers that are treated with a resinbinding adhesive to form a web having strong integrity and otherdesirable properties. The resulting assemblies, however, generally havepoor water-responsivity and are not suitable for flushable applications.The presence of binder also may result in undesirable properties in thefinal product, such as reduced sheet wettability, increased stiffness,stickiness, and higher production costs. It is also difficult to producea binder that will exhibit adequate wet strength during use and yetdisperse quickly upon disposal. Thus, nonwoven assemblies using thesebinders may either disintegrate slowly under ambient conditions or haveless than adequate wet strength properties in the presence of bodyfluids. To address this problem, pH and ion-sensitive water-dispersiblebinders, such as lattices containing acrylic or methacrylic acid with orwithout added salts, are known and described, for example, in U.S. Pat.No. 6,548,592 B1. Ion concentrations and pH levels in public sewerageand residential septic systems, however, can vary widely amonggeographical locations and may not be sufficient for the binder tobecome soluble and disperse. In this case, the fibrous articles will notdisintegrate after disposal and can clog drains or sewer laterals.

Multicomponent fibers containing a water-dispersible component and athermoplastic water non-dispersible component have been described, forexample, in U.S. Pat. Nos. 5,916,678; 5,405,698; 4,966,808; 5,525,282;5,366,804; 5,486,418. For example, these multicomponent fibers may be abicomponent fiber having a shaped or engineered transverse cross sectionsuch as, for example, an islands-in-the-sea, sheath core, side-by-side,or segmented pie configuration. The multicomponent fiber can besubjected to water or a dilute alkaline solution where thewater-dispersible component is dissolved away to leave the waternon-dispersible component behind as separate, independent fibers ofextremely small fineness. Polymers which have good water dispersibility,however, often impart tackiness to the resulting multicomponent fibers,which causes the fiber to stick together, block, or fuse during windingor storage after several days, especially under hot, humid conditions.To prevent fusing, often a fatty acid or oil-based finish is applied tothe surface of the fiber. In addition, large proportions of pigments orfillers are sometimes added to water dispersible polymers to preventfusing of the fibers as described, for example, in U.S. Pat. No.6,171,685. Such oil finishes, pigments, and fillers require additionalprocessing steps and can impart undesirable properties to the finalfiber. Many water-dispersible polymers also require alkaline solutionsfor their removal which can cause degradation of the other polymercomponents of the fiber such as, for example, reduction of inherentviscosity, tenacity, and melt strength. Further, some water-dispersiblepolymers can not withstand exposure to water during hydroentanglementand, thus, are not suitable for the manufacture of nonwoven webs andfabrics.

Alternatively, the water-dispersible component may serve as a bondingagent for the thermoplastic fibers in nonwoven webs. Upon exposure towater, the fiber to fiber bonds come apart such that the nonwoven webloses its integrity and breaks down into individual fibers. Thethermoplastic fiber components of these nonwoven webs, however, are notwater-dispersible and remain present in the aqueous medium and, thus,must eventually be removed from municipal wastewater treatment plants.Hydroentanglement may be used to produce disintegratable nonwovenfabrics without or with very low levels (<5 wt %) of added binder tohold the fibers together. Although these fabrics may disintegrate upondisposal, they often utilize fibers that are not water soluble orwater-dispersible and may result in entanglement and plugging withinsewer systems. Any added water-dispersible binders also must beminimally affected by hydroentangling and not form gelatinous buildup orcross-link, and thereby contribute to fabric handling or sewer relatedproblems.

A few water-soluble or water-dispersible polymers are available, but aregenerally not applicable to melt blown fiber forming operations or meltspinning in general. Polymers, such as polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylic acid are not melt processable as a resultof thermal decomposition that occurs at temperatures below the pointwhere a suitable melt viscosity is attained. High molecular weightpolyethylene oxide may have suitable thermal stability, but wouldprovide a high viscosity solution at the polymer interface resulting ina slow rate of disintegration. Water-dispersible sulfopolyesters havebeen described, for example, in U.S. Pat. Nos. 6,171,685; 5,543,488;5,853,701; 4,304,901; 6,211,309; 5,570,605; 6,428,900; and 3,779,993.Typical sulfopolyesters, however, are low molecular weightthermoplastics that are brittle and lack the flexibility to withstand awinding operation to yield a roll of material that does not fracture orcrumble. Sulfopolyesters also can exhibit blocking or fusing duringprocessing into film or fibers, which may require the use of oilfinishes or large amounts of pigments or fillers to avoid. Low molecularweight polyethylene oxide (more commonly known as polyethylene glycol)is a weak/brittle polymer that also does not have the required physicalproperties for fiber applications. Forming fibers from knownwater-soluble polymers via solution techniques is an alternative, butthe added complexity of removing solvent, especially water, increasesmanufacturing costs.

Accordingly, there is a need for a water-dispersible fiber and fibrousarticles prepared therefrom that exhibit adequate tensile strength,absorptivity, flexibility, and fabric integrity in the presence ofmoisture, especially upon exposure to human bodily fluids. In addition,a fibrous article is needed that does not require a binder andcompletely disperses or dissolves in residential or municipal seweragesystems. Potential uses include, but are not limited to, melt blownwebs, spunbond fabrics, hydroentangled fabrics, dry-laid non-wovens,bicomponent fiber components, adhesive promoting layers, binders forcellulosics, flushable nonwovens and films, dissolvable binder fibers,protective layers, and carriers for active ingredients to be released ordissolved in water. There is also a need for multicomponent fiber havinga water-dispersible component that does not exhibit excessive blockingor fusing of filaments during spinning operations, is easily removed byhot water at neutral or slightly acidic pH, and is suitable forhydroentangling processes to manufacture nonwoven fabrics. Otherextrudable and melt spun fibrous materials are also possible.

SUMMARY OF THE INVENTION

We have unexpectedly discovered that flexible, water-dispersible fibersmay be prepared from sulfopolyesters. Thus the present inventionprovides a water-dispersible fiber comprising:

-   (A) a sulfopolyester having a glass transistion temperature (Tg) of    at least 25° C., the sulfopolyester comprising:    -   (i) residues of one or more dicarboxylic acids;    -   (ii) about 4 to about 40 mole %, based on the total repeating        units, of residues of at least one sulfomonomer having 2        functional groups and one or more sulfonate groups attached to        an aromatic or cycloaliphatic ring wherein the functional groups        are hydroxyl, carboxyl, or a combination thereof;    -   (iii) one or more diol residues wherein at least 25 mole %,        based on the total diol residues, is a poly(ethylene glycol)        having a structure        H—(OCH2—CH2)n—OH        -   wherein n is an integer in the range of 2 to about 500; and    -   (iv) 0 to about 25 mole %, based on the total repeating units,        of residues of a branching monomer having 3 or more functional        groups wherein the functional groups are hydroxyl, carboxyl, or        a combination thereof;-   (B) optionally, a water-dispersible polymer blended with the    sulfopolyester; and-   (C) optionally, a water-nondispersible polymer blended with the    sulfopolyester with the proviso that the blend is an immiscible    blend;    wherein the fiber contains less than 10 weight percent of a pigment    or filler, based on the total weight of the fiber.    The fibers of the present invention may be unicomponent fibers that    rapidly disperse or dissolve in water and may be produced by    melt-blowing or melt-spinning. The fibers may be prepared from a    single sulfopolyester or a blend of the sulfopolyester with a    water-dispersible or water-nondispersible polymer. Thus, the fiber    of the present invention, optionally, may include a    water-dispersible polymer blended with the sulfopolyester. In    addition, the fiber may optionally include a water-nondispersible    polymer blended with the sulfopolyester, provided that the blend is    an immiscible blend. Our invention also includes fibrous articles    comprising our water-dispersible fibers. Thus, the fibers of our    invention may be used to prepare various fibrous articles, such as    yarns, melt-blown webs, spunbonded webs, and nonwoven fabrics that    are, in turn, water-dispersible or flushable. Staple fibers of our    invention can also be blended with natural or synthetic fibers in    paper, nonwoven webs, and textile yarns.

Another aspect of the present invention is a water-dispersible fibercomprising:

-   (A) a sulfopolyester having a glass transistion temperature (Tg) of    at least 25° C., the sulfopolyester comprising:    -   (i) about 50 to about 96 mole % of one or more residues of        isophthalic acid or terephthalic acid, based on the total acid        residues;    -   (ii) about 4 to about 30 mole %, based on the total acid        residues, of a residue of sodiosulfoisophthalic acid;    -   (iii) one or more diol residues wherein at least 25 mole %,        based on the total diol residues, is a poly(ethylene glycol)        having a structure        H—(OCH2—CH2)n—OH        -   wherein n is an integer in the range of 2 to about 500;    -   (iv) 0 to about 20 mole %, based on the total repeating units,        of residues of a branching monomer having 3 or more functional        groups wherein the functional groups are hydroxyl, carboxyl, or        a combination thereof;-   (B) optionally, a first water-dispersible polymer blended with the    sulfopolyester; and-   (C) optionally, a water-nondispersible polymer blended with the    sulfopolyester to form a blend with the proviso that the blend is an    immiscible blend;    wherein the fiber contains less than 10 weight percent of a pigment    or filler, based on the total weight of the fiber.    The water-dispersible, fibrous articles of the present invention    include personal care articles such as, for example, wipes, gauze,    tissue, diapers, training pants, sanitary napkins, bandages, wound    care, and surgical dressings. In addition to being    water-dispersible, the fibrous articles of our invention are    flushable, that is, compatible with and suitable for disposal in    residential and municipal sewerage systems.

The present invention also provides a multicomponent fiber comprising awater-dispersible sulfopolyester and one or more water non-dispersiblepolymers. The fiber has an engineered geometry such that the waternon-dispersible polymers are present as segments substantially isolatedfrom each other by the intervening sulfopolyester, which acts as abinder or encapsulating matrix for the water non-dispersible segments.Thus, another aspect of our invention is a multicomponent fiber having ashaped cross section, comprising:

-   -   A) a water dispersible sulfopolyester having a glass transistion        temperature (Tg) of at least 57° C., the sulfpolyester        comprising:        -   (i) residues of one or more dicarboxylic acids;        -   (ii) about 4 to about 40 mole %, based on the total            repeating units, of residues of at least one sulfomonomer            having 2 functional groups and one or more sulfonate groups            attached to an aromatic or cycloaliphatic ring wherein the            functional groups are hydroxyl, carboxyl, or a combination            thereof;        -   (iii) one or more diol residues wherein at least 25 mole %,            based on the total diol residues, is a poly(ethylene glycol)            having a structure            H—(OCH₂—CH₂)_(n)—OH            -   wherein n is an integer in the range of 2 to about 500;                and        -   (iv) 0 to about 25 mole %, based on the total repeating            units, of residues of a branching monomer having 3 or more            functional groups wherein the functional groups are            hydroxyl, carboxyl, or a combination thereof; and    -   B) a plurality of segments comprising one or more        water-nondispersable polymers immiscible with the        sulfopolyester, wherein the segments are substantially isolated        from each other by the sulfopolyester intervening between the        segments;    -   wherein the fiber contains less than 10 weight percent of a        pigment or filler, based on the total weight of the fiber.        The sulfopolyester has a glass transistion temperature of at        least 57° C. which greatly reduces blocking and fusion of the        fiber during winding and long term storage. The sulfopolyester        may be removed by contacting the multicomponent fiber with water        to leave behind the water non-dispersible segments as        microdenier fibers. Our invention, therefore, also provides a        process for microdenier fibers comprising:

-   A. spinning a water dispersible sulfopolyester having a glass    transistion temperature (Tg) of at least 57° C. and one or more    water-nondispersable polymers immiscible with the sulfopolyester    into multicomponent fibers, the sulfpolyester comprising:    -   (i) about 50 to about 96 mole % of one or more residues of        isophthalic acid or terephthalic acid, based on the total acid        residues;    -   (ii) about 4 to about 30 mole %, based on the total acid        residues, of a residue of sodiosulfoisophthalic acid;    -   (iii) one or more diol residues wherein at least 25 mole %,        based on the total diol residues, is a poly(ethylene glycol)        having a structure         H—(OCH₂—CH₂)_(n)—OH        -   wherein n is an integer in the range of 2 to about 500; and    -   (iv) 0 to about 20 mole %, based on the total repeating units,        of residues of a branching monomer having 3 or more functional        groups wherein the functional groups are hydroxyl, carboxyl, or        a combination thereof;    -   wherein the fibers have a plurality of segments comprising the        water-nondispersable polymers wherein the segments are        substantially isolated from each other by the sulfopolyester        intervening between the segments and the fibers contain less        than 10 weight percent of a pigment or filler, based on the        total weight of the fibers; and

-   B. contacting the multicomponent fibers with water to remove the    sulfopolyester thereby forming microdenier fibers.

The water non-dispersible polymers may be biodistintegratable asdetermined by DIN Standard 54900 and/or biodegradable as determined byASTM Standard Method, D6340-98. The multicomponent fiber also may beused to prepare a fibrous article such as a yarn, fabric, melt-blownweb, spun-bonded web, or non-woven fabric and which may comprise one ormore layers of fibers. The fibrous article having multicomponent fibers,in turn, may be contacted with water to produce fibrous articlescontaining microdenier fibers. Thus, another aspect of the invention isa process for a microdenier fiber web, comprising:

-   A. spinning a water dispersible sulfopolyester having a glass    transistion temperature (Tg) of at least 57° C. and one or more    water-nondispersable polymers immiscible with the sulfopolyester    into multicomponent fibers, the sulfpolyester comprising:    -   (i) about 50 to about 96 mole % of one or more residues of        isophthalic acid or terephthalic acid, based on the total acid        residues;    -   (ii) about 4 to about 30 mole %, based on the total acid        residues, of a residue of sodiosulfoisophthalic acid;    -   (iii) one or more diol residues wherein at least 25 mole %,        based on the total diol residues, is a poly(ethylene glycol)        having a structure        H—(OCH₂—CH₂)_(n)—OH        -   wherein n is an integer in the range of 2 to about 500; and    -   (iv) 0 to about 20 mole %, based on the total repeating units,        of residues of a branching monomer having 3 or more functional        groups wherein the functional groups are hydroxyl, carboxyl, or        a combination thereof,    -   wherein the multicomponent fibers have a plurality of segments        comprising the water-nondispersable polymers and the segments        are substantially isolated from each other by the sulfopolyester        intervening between the segments and the fibers contain less        than 10 weight percent of a pigment or filler, based on the        total weight of said fibers;-   B. overlapping and collecting the multicomponent fibers of Step A to    form a nonwoven web; and-   C. contacting the nonwoven web with water to remove the    sulfopolyester thereby forming a microdenier fiber web.

Our invention also provides a process for a process forwater-dispersible, nonwoven fabric comprising:

-   I. heating a water-dispersible polymer composition to a temperature    above its flow point, wherein the polymer composition comprises    -   (A) a sulfopolyester having a glass transistion temperature (Tg)        of at least 25° C., the sulfopolyester comprising:        -   (i) residues of one or more dicarboxylic acids;        -   (ii) about 4 to about 40 mole %, based on the total            repeating units, of residues of at least one sulfomonomer            having 2 functional groups and one or more metal sulfonate            groups attached to an aromatic or cycloaliphatic ring            wherein the functional groups are hydroxyl, carboxyl, or a            combination thereof;        -   (iii) one or more diol residues wherein at least 20 mole %,            based on the total diol residues, is a poly(ethylene glycol)            having a structure            H—(OCH2—CH2)n—OH            -   wherein n is an integer in the range of 2 to about 500;        -   (iv) 0 to about 25 mole %, based on the total repeating            units, of residues of a branching monomer having 3 or more            functional groups wherein the functional groups are            hydroxyl, carboxyl, or a combination thereof;    -   (B) optionally, a water-dispersible polymer blended with the        sulfopolyester; and    -   (C) optionally, a water-nondispersible polymer blended with the        sulfopolyester to form a blend with the proviso that the blend        is an immiscible blend;-   wherein the polymer composition contains less than 10 weight percent    of a pigment or filler, based on the total weight of the polymer    composition;-   II. melt spinning filaments; and-   III. overlapping and collecting the filaments of Step II to form a    nonwoven web.

Our invention thus offers a novel and inexpensive process for awater-dispersible nonwoven fabric by melt-spinning a water-dispersiblesulfopolyester and forming a nonwoven web. The nonwoven fabric may be inthe form of a flat fabric or a 3-dimensional shape and may beincorporated into a variety of fibrous articles such as the personalcare articles noted hereinabove or used for the manufacture ofwater-dispersible and/or flushable protective outerware such as, forexample, surgical gowns and protective clothing for chemical andbiohazard cleanup and laboratory work.

DETAILED DESCRIPTION

The present invention provides water-dispersible fibers and fibrousarticles that show tensile strength, absorptivity, flexibility, andfabric integrity in the presence of moisture, especially upon exposureto human bodily fluids. The fibers and fibrous articles of our inventiondo not require the presence of oil, wax, or fatty acid finishes or theuse of large amounts (typically 10 wt % or greater) of pigments orfillers to prevent blocking or fusing of the fibers during processing.In addition, the fibrous articles prepared from our novel fibers do notrequire a binder and readily disperse or dissolve in home or publicsewerage systems. In a general embodiment, our invention provides awater-dispersible fiber comprising a sulfopolyester having a glasstransistion temperature (Tg) of at least 25° C., wherein thesulfpolyester comprises: (i) residues of one or more dicarboxylic acids;(ii) about 4 to about 40 mole %, based on the total repeating units, ofresidues of at least one sulfomonomer having 2 functional groups and oneor more sulfonate groups attached to an aromatic or cycloaliphatic ringwherein the functional groups are hydroxyl, carboxyl, or a combinationthereof; (iii) one or more diol residues wherein at least 25 mole %,based on the total diol residues, is a poly(ethylene glycol) having astructureH—(OCH₂—CH₂)_(n)—OHwherein n is an integer in the range of 2 to about 500; and (iv) 0 toabout 25 mole %, based on the total repeating units, of residues of abranching monomer having 3 or more functional groups wherein thefunctional groups are hydroxyl, carboxyl, or a combination thereof. Ourfiber may optionally include a water-dispersible polymer blended withthe sulfopolyester and, optionally, a water-nondispersible polymerblended with the sulfopolyester with the proviso that the blend is animmiscible blend. Our fiber contains less than 10 weight percent of apigment or filler, based on the total weight of the fiber. The presentinvention also includes fibrous articles comprising these fibers and mayinclude personal care products such as wipes, gauze, tissue, diapers,adult incontinence briefs, training pants, sanitary napkins, bandages,and surgical dressings. The fibrous articles may have one or moreabsorbent layers of fibers.

The fibers of our invention may be unicomponent fibers, bicomponent ormulticomponent fibers. For example, the fibers of the present inventionmay be prepared by melt spinning a single sulfopolyester orsulfopolyester blend and include staple, monofilament, and multifilamentfibers with a shaped cross-section. In addition, our invention providesmulticomponent fibers, such as described, for example, in U.S. Pat. No.5,916,678, which may be prepared by extruding the sulfopolyester and oneor more water non-dispersible polymers, which are immiscible with thesulfopolyester, separately through a spinneret having a shaped orengineered tranverse geometry such as, for example, an“islands-in-the-sea”, sheath-core, side-by-side, or segmented pieconfiguration. The sulfopolyester may be later removed by dissolving theinterfacial layers or pie segments and leaving the smaller filaments ormicrodenier fibers of the water non-dispersible polymer(s). For example,the sulfopolyester and water non-dispersible polymers may be fed to apolymer distribution system where the polymers are introduced into asegmented spinneret plate. The polymers follow separate paths to thefiber spinneret and are combined at the spinneret hole which compriseseither two concentric circular holes thus providing a sheath-core typefiber, or a circular spinneret hole divided along a diameter intomultiple parts to provide a fiber having a side-by-side type.Alternatively, the immiscible water dispersible sulfopolyester and waternon-dispersible polymers may be introduced separately into a spinnerethaving a plurality of radial channels to produce a multicomponent fiberhaving a segmented pie cross section. Typically, the sulfopolyester willform the “sheath” component of a sheath core configuration. In fibercross sections having a plurality of segments, the water non-dispersiblesegments, typically, are substantially isolated from each other by thesulfopolyester. Alternatively, multicomponent fibers may be formed bymelting the sulfopolyester and water non-dispersible polymers inseparate extruders and directing the the polymer flows into onespinneret with a plurality of distribution flow paths in form of smallthin tubes or segments to provide a fiber having an islands-in-the-seashaped cross section. An example of such a spinneret is described inU.S. Pat. No. 5,366,804. In the present invention, typically, thesulfopolyester will form the “sea” component and the waternon-dispersible polymer will for the “islands” component.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth used in the specification and claims are to be understoodas being modified in all instances by the term “about.” Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe following specification and attached claims are approximations thatmay vary depending upon the desired properties sought to be obtained bythe present invention. At the very least, each numerical parametershould at least be construed in light of the number of reportedsignificant digits and by applying ordinary rounding techniques.Further, the ranges stated in this disclosure and the claims areintended to include the entire range specifically and not just theendpoint(s). For example, a range stated to be 0 to 10 is intended todisclose all whole numbers between 0 and 10 such as, for example 1, 2,3, 4, etc., all fractional numbers between 0 and 10, for example 1.5,2.3, 4.57, 6.1113, etc., and the endpoints 0 and 10. Also, a rangeassociated with chemical substituent groups such as, for example, “C1 toC5 hydrocarbons”, is intended to specifically include and disclose C1and C5 hydrocarbons as well as C2, C3, and C4 hydrocarbons.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements.

The unicomponent fibers and fibrous articles of the present inventionare water-dispersible and, typically, completely disperse at roomtemperature. Higher water temperatures can be used to accelerate theirdispersibility or rate of removal from the nonwoven or multicomponentfiber. The term “water-dispersible”, as used herein with respect tounicomponent fibers and fibrous articles prepared from unicomponentfibers, is intended to be synonymous with the terms“water-dissipatable”, “water-disintegratable”, “water-dissolvable”,“water-dispellable”, “water soluble”, “water-removable”, “hydrosoluble”,and “hydrodispersible” and is intended to mean that the fiber or fibrousarticle is therein or therethrough dispersed or dissolved by the actionof water. The terms “dispersed”, “dispersible”, “dissipate”, or“dissipatable” mean that, using a sufficient amount of deionized water(e.g., 100:1 water:fiber by weight) to form a loose suspension or slurryof the fibers or fibrous article, at a temperature of about 60° C., andwithin a time period of up to 5 days, the fiber or fibrous articledissolves, disintegrates, or separates into a plurality of incoherentpieces or particles distributed more or less throughout the medium suchthat no recognizable filaments are recoverable from the medium uponremoval of the water, for example, by filtration or evaporation. Thus,“water-dispersible”, as used herein, is not intended to include thesimple disintegration of an assembly of entangled or bound, butotherwise water insoluble or nondispersible, fibers wherein the fiberassembly simply breaks apart in water to produce a slurry of fibers inwater which could be recovered by removal of the water. In the contextof this invention, all of these terms refer to the activity of water ora mixture of water and a water-miscible cosolvent on the sulfopolyestersdescribed herein. Examples of such water-miscible cosolvents includesalcohols, ketones, glycol ethers, esters and the like. It is intendedfor this terminology to include conditions where the sulfopolyester isdissolved to form a true solution as well as those where thesulfopolyester is dispersed within the aqueous medium. Often, due to thestatistical nature of sulfopolyester compositions, it is possible tohave a soluble fraction and a dispersed fraction when a singlesulfopolyester sample is placed in an aqueous medium.

Similarly, the term “water-dispersible”, as used herein in reference tothe sulfopolyester as one component of a multicomponent fiber or fibrousarticle, also is intended to be synonymous with the terms“water-dissipatable”, “water-disintegratable”, “water-dissolvable”,“water-dispellable”, “water soluble”, “water-removable”,“hydro-soluble”, and “hydrodispersible” and is intended to mean that thesulfopolyester component is sufficiently removed from the multicomponentfiber and is dispersed or dissolved by the action of water to enable therelease and separation of the water non-dispersible fibers containedtherein. The terms “dispersed”, “dispersible”, “dissipate”, or“dissipatable” mean that, using a sufficient amount of deionized water(e.g., 100:1 water:fiber by weight) to form a loose suspension or slurryof the fibers or fibrous article, at a temperature of about 60° C., andwithin a time period of up to 5 days, sulfopolyester componentdissolves, disintegrates, or separates from the multicomponent fiber,leaving behind a plurality of microdenier fibers from the waternon-dispersible segments.

The water-dispersible fiber of the present invention is prepared frompolyesters or, more specifically sulfopolyesters, comprisingdicarboxylic acid monomer residues, sulfomonomer residues, diol monomerresidues, and repeating units. The sulfomonomer may be a dicarboxylicacid, a diol, or hydroxycarboxylic acid. Thus, the term “monomerresidue”, as used herein, means a residue of a dicarboxylic acid, adiol, or a hydroxycarboxylic acid. A “repeating unit”, as used herein,means an organic structure having 2 monomer residues bonded through acarbonyloxy group. The sulfopolyesters of the present invention containsubstantially equal molar proportions of acid residues (100 mole %) anddiol residues (100 mole %) which react in substantially equalproportions such that the total moles of repeating units is equal to 100mole %. The mole percentages provided in the present disclosure,therefore, may be based on the total moles of acid residues, the totalmoles of diol residues, or the total moles of repeating units. Forexample, a sulfopolyeseter containing 30 mole % of a sulfomonomer, whichmay be a dicarboxylic acid, a diol, or hydroxycarboxylic acid, based onthe total repeating units, means that the sulfopolyester contains 30mole % sulfomonomer out of a total of 100 mole % repeating units. Thus,there are 30 moles of sulfomonomer residues among every 100 moles ofrepeating units. Similarly, a sulfopolyeseter containing 30 mole % of adicarboxylic acid sulfomonomer, based on the total acid residues, meansthe sulfopolyester contains 30 mole % sulfomonomer out of a total of 100mole % acid residues. Thus, in this latter case, there are 30 moles ofsulfomonomer residues among every 100 moles of acid residues.

The sulfopolyesters described herein have an inherent viscosity,abbreviated hereinafter as “Ih.V.”, of at least about 0.1 dL/g,preferably about 0.2 to 0.3 dL/g, and most preferably greater than about0.3 dL/g, measured in a 60/40 parts by weight solution ofphenol/tetrachloroethane solvent at 25° C. and at a concentration ofabout 0.5 g of sulfopolyester in 100 mL of solvent. The term“polyester”, as used herein, encompasses both “homopolyesters” and“copolyesters” and means a synthetic polymer prepared by thepolycondensation of difunctional carboxylic acids with difunctionalhydroxyl compound. As used herein, the term “sulfopolyester” means anypolyester comprising a sulfomonomer. Typically the difunctionalcarboxylic acid is a dicarboxylic acid and the difunctional hydroxylcompound is a dihydric alcohol such as, for example glycols and diols.Alternatively, the difunctional carboxylic acid may be a hydroxycarboxylic acid such as, for example, p-hydroxybenzoic acid, and thedifunctional hydroxyl compound may be a aromatic nucleus bearing 2hydroxy substituents such as, for example, hydroquinone. The term“residue”, as used herein, means any organic structure incorporated intothe polymer through a polycondensation reaction involving thecorresponding monomer. Thus, the dicarboxylic acid residue may bederived from a dicarboxylic acid monomer or its associated acid halides,esters, salts, anhydrides, or mixtures thereof. As used herein,therefore, the term dicarboxylic acid is intended to includedicarboxylic acids and any derivative of a dicarboxylic acid, includingits associated acid halides, esters, half-esters, salts, half-salts,anhydrides, mixed anhydrides, or mixtures thereof, useful in apolycondensation process with a diol to make a high molecular weightpolyester.

The sulfopolyester of the present invention includes one or moredicarboxylic acid residues. Depending on the type and concentration ofthe sulfomonomer, the dicarboxylic acid residue may comprise from about60 to about 100 mole % of the acid residues. Other examples ofconcentration ranges of dicarboxylic acid residues are from about 60mole % to about 95 mole %, and about 70 mole % to about 95 mole %.Examples of dicarboxylic acids that may be used include aliphaticdicarboxylic acids, alicyclic dicarboxylic acids, aromatic dicarboxylicacids, or mixtures of two or more of these acids. Thus, suitabledicarboxylic acids include, but are not limited to succinic; glutaric;adipic; azelaic; sebacic; fumaric; maleic; itaconic;1,3-cyclohexanedicarboxylic; 1,4-cyclohexanedicarboxylic; diglycolic;2,5-norbornanedicarboxylic; phthalic; terephthalic;1,4-naphthalenedicarboxylic; 2,5-naphthalenedicarboxylic; diphenic;4,4′-oxydibenzoic; 4,4′-sulfonyidibenzoic; and isophthalic. Thepreferred dicarboxylic acid residues are isophthalic, terephthalic, and1,4-cyclohexanedicarboxylic acids, or if diesters are used, dimethylterephthalate, dimethyl isophthalate, anddimethyl-1,4-cyclohexane-dicarboxylate with the residues of isophthalicand terephthalic acid being especially preferred. Although thedicarboxylic acid methyl ester is the most preferred embodiment, it isalso acceptable to include higher order alkyl esters, such as ethyl,propyl, isopropyl, butyl, and so forth. In addition, aromatic esters,particularly phenyl, also may be employed.

The sulfopolyester includes about 4 to about 40 mole %, based on thetotal repeating units, of residues of at least one sulfomonomer having 2functional groups and one or more sulfonate groups attached to anaromatic or cycloaliphatic ring wherein the functional groups arehydroxyl, carboxyl, or a combination thereof. Additional examples ofconcentration ranges for the sulfomonomer residues are about 4 to about35 mole %, about 8 to about 30 mole %, and about 8 to about 25 mole %,based on the total repeating units. The sulfomonomer may be adicarboxylic acid or ester thereof containing a sulfonate group, a diolcontaining a sulfonate group, or a hydroxy acid containing a sulfonategroup. The term “sulfonate” refers to a salt of a sulfonic acid havingthe structure “—SO₃M” wherein M is the cation of the sulfonate salt. Thecation of the sulfonate salt may be a metal ion such as Li⁺, Na⁺, K⁺,Mg⁺⁺, Ca⁺⁺, Ni⁺⁺, Fe⁺⁺, and the like. Alternatively, the cation of thesulfonate salt may be non-metallic such as a nitrogenous base asdescribed, for example, in U.S. Pat. No. 4,304,901. Nitrogen-basedcations are derived from nitrogen-containing bases, which may bealiphatic, cycloaliphatic, or aromatic compounds. Examples of suchnitrogen containing bases include ammonia, dimethylethanolamine,diethanolamine, triethanolamine, pyridine, morpholine, and piperidine.Because monomers containing the nitrogen-based sulfonate salts typicallyare not thermally stable at conditions required to make the polymers inthe melt, the method of this invention for preparing sulfopolyesterscontaining nitrogen-based sulfonate salt groups is to disperse,dissipate, or dissolve the polymer containing the required amount ofsulfonate group in the form of its alkali metal salt in water and thenexchange the alkali metal cation for a nitrogen-based cation.

When a monovalent alkali metal ion is used as the cation of thesulfonate salt, the resulting sulfopolyester is completely dispersiblein water with the rate of dispersion dependent on the content ofsulfomonomer in the polymer, temperature of the water, surfacearea/thickness of the sulfopolyester, and so forth. When a divalentmetal ion is used, the resulting sulfopolyesters are not readilydispersed by cold water but are more easily dispersed by hot water.Utilization of more than one counterion within a single polymercomposition is possible and may offer a means to tailor or fine-tune thewater-responsivity of the resulting article of manufacture. Examplessulfomonomers residues include monomer residues where the sulfonate saltgroup is attached to an aromatic acid nucleus, such as, for example,benzene; naphthalene; diphenyl; oxydiphenyl; sulfonyldiphenyl; andmethylenediphenyl or cycloaliphatic rings, such as, for example,cyclohexyl; cyclopentyl; cyclobutyl; cycloheptyl; and cyclooctyl. Otherexamples of sulfomonomer residues which may be used in the presentinvention are the metal sulfonate salt of sulfophthalic acid,sulfoterephthalic acid, sulfoisophthalic acid, or combinations thereof.Other examples of sulfomonomers which may be used are5-sodiosulfoisophthalic acid and esters thereof. If the sulfomonomerresidue is from 5-sodiosulfoisophthalic acid, typical sulfomonomerconcentration ranges are about 0.4 to about 35 mole %, about 8 to about30 mole %, and about 8 to 25 mole %, based on the total moles of acidresidues.

The sulfomonomers used in the preparation of the sulfopolyesters areknown compounds and may be prepared using methods well known in the art.For example, sulfomonomers in which the sulfonate group is attached toan aromatic ring may be prepared by sulfonating the aromatic compoundwith oleum to obtain the corresponding sulfonic acid and followed byreaction with a metal oxide or base, for example, sodium acetate, toprepare the sulfonate salt. Procedures for preparation of varioussulfomonomers are described, for example, in U.S. Pat. Nos. 3,779,993;3,018,272; and 3,528,947.

It is also possible to prepare the polyester using, for example, asodium sulfonate salt, and ion-exchange methods to replace the sodiumwith a different ion, such as zinc, when the polymer is in the dispersedform. This type of ion exchange procedure is generally superior topreparing the polymer with divalent salts insofar as the sodium saltsare usually more soluble in the polymer reactant melt-phase.

The sulfopolyester includes one or more diol residues which may includealiphatic, cycloaliphatic, and aralkyl glycols. The cycloaliphaticdiols, for example, 1,3- and 1,4-cyclohexanedimethanol, may be presentas their pure cis or trans isomers or as a mixture of cis and transisomers. As used herein, the term “diol” is synonymous with the term“glycol” and means any dihydric alcohol. Examples diols include ethyleneglycol; diethylene glycol; triethylene glycol; polyethylene glycols;1,3-propanediol; 2,4-dimethyl-2-ethylhexane-1,3-diol;2,2-dimethyl-1,3-propanediol; 2-ethyl-2-butyl-1,3-propanediol;2-ethyl-2-isobutyl-1,3-propanediol; 1,3-butanediol; 1,4-butanediol;1,5-pentanediol; 1,6-hexanediol; 2,2,4-trimethyl-1,6-hexanediol;thiodiethanol; 1,2-cyclohexanedimethanol; 1,3-cyclohexanedimethanol;1,4-cyclohexanedimethanol; 2,2,4,4-tetramethyl-1,3-cyclobutanediol;p-xylylenediol, or combinations of one or more of these glycols.

The diol residues may include from about 25 mole % to about 100 mole %,based on the total diol residues, of residue of a poly(ethylene glycol)having a structureH—(OCH₂—CH₂)_(n)—OHwherein n is an integer in the range of 2 to about 500. Non-limitingexamples of lower molecular weight polyethylene glycols, e.g., wherein nis from 2 to 6, are diethylene glycol, triethylene glycol, andtetraethylene glycol. Of these lower molecular weight glycols,diethylene and triethylene glycol are most preferred. Higher molecularweight polyethylene glycols (abbreviated herein as “PEG”), wherein n isfrom 7 to about 500, include the commercially available products knownunder the designation CARBOWAX®, a product of Dow Chemical Company(formerly Union Carbide). Typically, PEG's are used in combination withother diols such as, for example, diethylene glycol or ethylene glycol.Based on the values of n, which range from greater than 6 to 500, themolecular weight may range from greater than 300 to about 22,000 g/mol.The molecular weight and the mole % are inversely proportional to eachother; specifically, as the molecular weight is increased, the mole %will be decreased in order to achieve a designated degree ofhydrophilicity. For example, it is illustrative of this concept toconsider that a PEG having a molecular weight of 1000 may constitute upto 10 mole % of the total diol, while a PEG having a molecular weight of10,000 would typically be incorporated at a level of less than 1 mole %of the total diol.

Certain dimer, trimer, and tetramer diols may be formed in situ due toside reactions that may be controlled by varying the process conditions.For example, varying amounts of diethylene, triethylene, andtetraethylene glycols may be formed from ethylene glycol from anacid-catalyzed dehydration reaction which occurs readily when thepolycondensation reaction is carried out under acidic conditions. Thepresence of buffer solutions, well-known to those skilled in the art,may be added to the reaction mixture to retard these side reactions.Additional compositional latitude is possible, however, if the buffer isomitted and the dimerization, trimerization, and tetramerizationreactions are allowed to proceed.

The sulfopolyester of the present invention may include from 0 to about25 mole %, based on the total repeating units, of residues of abranching monomer having 3 or more functional groups wherein thefunctional groups are hydroxyl, carboxyl, or a combination thereof.Non-limiting examples of branching monomers are 1,1,1-trimethylolpropane, 1,1,1-trimethylolethane, glycerin, pentaerythritol, erythritol,threitol, dipentaerythritol, sorbitol, trimellitic anhydride,pyromellitic dianhydride, dimethylol propionic acid, or combinationsthereof. Further examples of branching monomer concentration ranges arefrom 0 to about 20 mole % and from 0 to about 10 mole %. The presence ofa branching monomer may result in a number of possible benefits to thesulfopolyester of the present invention, including but not limited to,the ability to tailor rheological, solubility, and tensile properties.For example, at a constant molecular weight, a branched sulfopolyester,compared to a linear analog, will also have a greater concentration ofend groups that may facilitate post-polymerization crosslinkingreactions. At high concentrations of branching agent, however, thesulfopolyester may be prone to gelation.

The sulfopolyester used for the fiber of the present invention has aglass transition temperature, abbreviated herein as “Tg”, of at least25° C. as measured on the dry polymer using standard techniques, such asdifferentical scanning calorimetry (“DSC”), well known to personsskilled in the art. The Tg measurements of the sulfopolyesters of thepresent invention are conducted using a “dry polymer”, that is, apolymer sample in which adventitious or absorbed water is driven off byheating to polymer to a temperature of about 200° C. and allowing thesample to return to room temperature. Typically, the sulfopolyester isdried in the DSC apparatus by conducting a first thermal scan in whichthe sample is heated to a temperature above the water vaporizationtemperature, holding the sample at that temperature until thevaporization of the water absorbed in the polymer is complete (asindicated by an a large, broad endotherm), cooling the sample to roomtemperature, and then conducting a second thermal scan to obtain the Tgmeasurement. Further examples of glass transition temperatures exhibitedby the sulfopolyester are at least 30° C., at least 35° C., at least 40°C., at least 50° C., at least 60° C., at least 65° C., at least 80° C.,and at least 90° C. Although other Tg's are possible, typical glasstransition temperatures of the dry sulfopolyesters our invention areabout 30° C., about 48° C., about 55° C., about 65° C., about 70° C.,about 75° C., about 85° C., and about 90° C.

Our novel fibers may consist essentially of or, consist of, thesulfopolyesters described hereinabove. In another embodiment, however,the sulfopolyesters of this invention may be a single polyester or maybe blended with one or more supplemental polymers to modify theproperties of the resulting fiber. The supplemental polymer may or maynot be water-dispersible depending on the application and may bemiscible or immiscible with the sulfopolyester. If the supplementalpolymer is water-nondispersible, it is preferred that the blend with thesulfopolyester is immiscible. The term “miscible”, as used herein, isintended to mean that the blend has a single, homogeneous amorphousphase as indicated by a single composition-dependent Tg. For example, afirst polymer that is miscible with second polymer may be used to“plasticize” the second polymer as illustrated, for example, in U.S.Pat. No. 6,211,309. By contrast, the term “immiscible”, as used herein,denotes a blend that shows at least 2, randomly mixed, phases andexhibits more than one Tg. Some polymers may be immiscible and yetcompatible with the sulfopolyester. A further general description ofmiscible and immiscible polymer blends and the various analyticaltechniques for their characterization may be found in Polymer BlendsVolumes 1 and 2, Edited by D. R. Paul and C. B. Bucknall, 2000, JohnWiley & Sons, Inc.

Non-limiting examples of water-dispersible polymers that may be blendedwith the sulfopolyester are polymethacrylic acid, polyvinyl pyrrolidone,polyethylene-acrylic acid copolymers, polyvinyl methyl ether, polyvinylalcohol, polyethylene oxide, hydroxy propyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, ethyl hydroxyethyl cellulose,isopropyl cellulose, methyl ether starch, polyacrylamides, poly(N-vinylcaprolactam), polyethyl oxazoline, poly(2-isopropyl-2-oxazoline),polyvinyl methyl oxazolidone, water-dispersible sulfopolyesters,polyvinyl methyl oxazolidimone, poly(2,4-dimethyl-6-triazinylethylene),and ethylene oxide-propylene oxide copolymers. Examples of polymerswhich are water-nondispersible that may be blended with thesulfopolyester include, but are not limited to, polyolefins, such ashomo- and copolymers of polyethylene and polypropylene; poly(ethyleneterephthalate); poly(butylene terephthalate); and polyamides, such asnylon-6; polylactides; caprolactone; Eastar Bio® (poly(tetramethyleneadipate-co-terephthalate), a product of Eastman Chemical Company);polycarbonate; polyurethane; and polyvinyl chloride.

According to our invention, blends of more than one sulfopolyester maybe used to tailor the end-use properties of the resulting fiber orfibrous article, for example, a nonwoven fabric or web. The blends ofone or more sulfopolyesters will have Tg's of at least 25° C. for thewater-dispersible, unicomponent fibers and at least 57° C. for themulticomponent fibers. Thus, blending may also be exploited to alter theprocessing characteristics of a sulfopolyester to facilitate thefabrication of a nonwoven. In another example, an immiscible blend ofpolypropylene and sulfopolyester may provide a conventional nonwoven webthat will break apart and completely disperse in water as truesolubility is not needed. In this latter example, the desiredperformance is related to maintaining the physical properties of thepolypropylene while the sulfopolyester is only a spectator during theactual use of the product or, alternatively, the sulfopolyester isfugitive and is removed before the final form of the product isutilized.

The sulfopolyester and supplemental polymer may be blended in batch,semicontinuous, or continuous processes. Small scale batches may bereadily prepared in any high-intensity mixing devices well-known tothose skilled in the art, such as Banbury mixers, prior to melt-spinningfibers. The components may also be blended in solution in an appropriatesolvent. The melt blending method includes blending the sulfopolyesterand supplemental polymer at a temperature sufficient to melt thepolymers. The blend may be cooled and pelletized for further use or themelt blend can be melt spun directly from this molten blend into fiberform. The term “melt” as used herein includes, but is not limited to,merely softening the polyester. For melt mixing methods generally knownin the polymers art, see Mixing and Compounding of Polymers (I.Manas-Zloczower & Z. Tadmor editors, Carl Hanser Verlag Publisher, 1994,New York, N.Y.).

Our invention also provides a water-dispersible fiber comprising asulfopolyester having a glass transistion temperature (Tg) of at least25° C., wherein the sulfpolyester comprises: (i) about 50 to about 96mole % of one or more residues of isophthalic acid or terephthalic acid,based on the total acid residues; (ii) about 4 to about 30 mole %, basedon the total acid residues, of a residue of sodiosulfoisophthalic acid;(iii) one or more diol residues wherein at least 25 mole %, based on thetotal diol residues, is a poly(ethylene glycol) having a structureH—(OCH₂—CH₂)_(n)—OHwherein n is an integer in the range of 2 to about 500; (iv) 0 to about20 mole %, based on the total repeating units, of residues of abranching monomer having 3 or more functional groups wherein thefunctional groups are hydroxyl, carboxyl, or a combination thereof. Asdescribed hereinabove, the fiber may optionally include a firstwater-dispersible polymer blended with the sulfopolyester; and,optionally, a water-nondispersible polymer blended with thesulfopolyester such that the blend is an immiscible blend. Our fibercontains less than 10 weight percent of a pigment or filler, based onthe total weight of the fiber. The first water-dispersible polymer is asdescribed hereinabove. The sulfopolyester should have a glass transitiontemperature (Tg) of at least 25° C., but may have, for example, a Tg ofabout 35° C., about 48° C., about 55° C., about 65° C., about 70° C.,about 75° C., about 85° C., and about 90° C. The sulfopolyester maycontain other concentrations of isophthalic acid residues, for example,about 60 to about 95 mole %, and about 75 to about 95 mole %. Furtherexamples of isophthalic acid residue concentrations ranges are about 70to about 85 mole %, about 85 to about 95 mole % and about 90 to about 95mole %. The sulfopolyester also may comprise about 25 to about 95 mole %of the residues of diethylene glycol. Further examples of diethyleneglycol residue concentration ranges include about 50 to about 95 mole %,about 70 to about 95 mole %, and about 75 to about 95 mole %. Thesulfopolyester also may include the residues of ethylene glycol and/or1,4-cyclohexanedimethanol, abbreviated herein as “CHDM”. Typicalconcentration ranges of CHDM residues are about 10 to about 75 mole %,about 25 to about 65 mole %, and about 40 to about 60 mole %. Typicalconcentration ranges of ethylene glycol residues are are about 10 toabout 75 mole %, about 25 to about 65 mole %, and about 40 to about 60mole %. In another embodiment, the sulfopolyester comprises is about 75to about 96 mole % of the residues of isophthalic acid and about 25 toabout 95 mole % of the residues of diethylene glycol.

The sulfopolyesters of the instant invention are readily prepared fromthe appropriate dicarboxylic acids, esters, anhydrides, or salts,sulfomonomer, and the appropriate diol or diol mixtures using typicalpolycondensation reaction conditions. They may be made by continuous,semi-continuous, and batch modes of operation and may utilize a varietyof reactor types. Examples of suitable reactor types include, but arenot limited to, stirred tank, continuous stirred tank, slurry, tubular,wiped-film, falling film, or extrusion reactors. The term “continuous”as used herein means a process wherein reactants are introduced andproducts withdrawn simultaneously in an uninterrupted manner. By“continuous” it is meant that the process is substantially or completelycontinuous in operation and is to be contrasted with a “batch” process.“Continuous” is not meant in any way to prohibit normal interruptions inthe continuity of the process due to, for example, start-up, reactormaintenance, or scheduled shut down periods. The term “batch” process asused herein means a process wherein all the reactants are added to thereactor and then processed according to a predetermined course ofreaction during which no material is fed or removed into the reactor.The term “semicontinuous” means a process where some of the reactantsare charged at the beginning of the process and the remaining reactantsare fed continuously as the reaction progresses. Alternatively, asemicontinuous process may also include a process similar to a batchprocess in which all the reactants are added at the beginning of theprocess except that one or more of the products are removed continuouslyas the reaction progresses. The process is operated advantageously as acontinuous process for economic reasons and to produce superiorcoloration of the polymer as the sulfopolyester may deteriorate inappearance if allowed to reside in a reactor at an elevated temperaturefor too long a duration.

The sulfopolyesters of the present invention are prepared by proceduresknown to persons skilled in the art. The sulfomonomer is most oftenadded directly to the reaction mixture from which the polymer is made,although other processes are known and may also be employed, forexample, as described in U.S. Pat. Nos. 3,018,272, 3,075,952, and3,033,822. The reaction of the sulfomonomer, diol component and thedicarboxylic acid component may be carried out using conventionalpolyester polymerization conditions. For example, when preparing thesulfopolyesters by means of an ester interchange reaction, i.e., fromthe ester form of the dicarboxylic acid components, the reaction processmay comprise two steps. In the first step, the diol component and thedicarboxylic acid component, such as, for example, dimethylisophthalate, are reacted at elevated temperatures, typically, about150° C. to about 250° C. for about 0.5 to about 8 hours at pressuresranging from about 0.0 kPa gauge to about 414 kPa gauge (60 pounds persquare inch, “psig”). Preferably, the temperature for the esterinterchange reaction ranges from about 180° C. to about 230° C. forabout 1 to about 4 hours while the preferred pressure ranges from about103 kPa gauge (15 psig) to about 276 kPa gauge (40 psig). Thereafter,the reaction product is heated under higher temperatures and underreduced pressure to form sulfopolyester with the elimination of diol,which is readily volatilized under these conditions and removed from thesystem. This second step, or polycondensation step, is continued underhigher vacuum and a temperature which generally ranges from about 230°C. to about 350° C., preferably about 250° C. to about 310° C. and mostpreferably about 260° C. to about 290° C. for about 0.1 to about 6hours, or preferably, for about 0.2 to about 2 hours, until a polymerhaving the desired degree of polymerization, as determined by inherentviscosity, is obtained. The polycondensation step may be conducted underreduced pressure which ranges from about 53 kPa (400 torr) to about0.013 kPa (0.1 torr). Stirring or appropriate conditions are used inboth stages to ensure adequate heat transfer and surface renewal of thereaction mixture. The reactions of both stages are facilitated byappropriate catalysts such as, for example, alkoxy titanium compounds,alkali metal hydroxides and alcoholates, salts of organic carboxylicacids, alkyl tin compounds, metal oxides, and the like. A three-stagemanufacturing procedure, similar to that described in U.S. Pat. No.5,290,631, may also be used, particularly when a mixed monomer feed ofacids and esters is employed.

To ensure that the reaction of the diol component and dicarboxylic acidcomponent by an ester interchange reaction mechanism is driven tocompletion, it is preferred to employ about 1.05 to about 2.5 moles ofdiol component to one mole dicarboxylic acid component. Persons of skillin the art will understand, however, that the ratio of diol component todicarboxylic acid component is generally determined by the design of thereactor in which the reaction process occurs.

In the preparation of sulfopolyester by direct esterification, i.e.,from the acid form of the dicarboxylic acid component, sulfopolyestersare produced by reacting the dicarboxylic acid or a mixture ofdicarboxylic acids with the diol component or a mixture of diolcomponents. The reaction is conducted at a pressure of from about 7 kPagauge (1 psig) to about 1379 kPa gauge (200 psig), preferably less than689 kPa (100 psig) to produce a low molecular weight, linear or branchedsulfopolyester product having an average degree of polymerization offrom about 1.4 to about 10. The temperatures employed during the directesterification reaction typically range from about 180° C. to about 280°C., more preferably ranging from about 220° C. to about 270° C. This lowmolecular weight polymer may then be polymerized by a polycondensationreaction.

The water dispersible and multicomponent fibers and fibrous articles ofthis invention also may contain other conventional additives andingredients which do not deleteriously affect their end use. Forexample, additives such as fillers, surface friction modifiers, lightand heat stabilizers, extrusion aids, antistatic agents, colorants,dyes, pigments, fluorescent brighteners, antimicrobials,anticounterfeiting markers, hydrophobic and hydrophilic enhancers,viscosity modifiers, slip agents, tougheners, adhesion promoters, andthe like may be used. The fibers and fibrous articles of our inventiondo not require the presence of additives such as, for example, pigments,fillers, oils, waxes, or fatty acid finishes, to prevent blocking orfusing of the fibers during processing. The terms “blocking or fusing”,as used herein, is understood to mean that the fibers or fibrousarticles stick together or fuse into a mass such that the fiber cannotbe processed or used for its intended purpose. Blocking and fusing canoccur during processing of the fiber or fibrous article or duringstorage over a period of days or weeks and is exacerbated under hot,humid conditions. In one embodiment of the invention, the fibers andfibrous articles will contain less than 10 wt % of such anti-blockingadditives, based on the total weight of the fiber or fibrous article.For example, the fibers and fibrous articles may contain less than 10 wt% of a pigment or filler. In other examples, the fibers and fibrousarticles may contain less than 9 wt %, less than 5 wt %, less than 3 wt%, less than 1 wt %, and 0 wt % of a pigment or filler, based on thetotal weight of the fiber. Colorants, sometimes referred to as toners,may be added to impart a desired neutral hue and/or brightness to thesulfopolyester. When colored fibers are desired, pigments or colorantsmay be included in the sulfopolyester reaction mixture during thereaction of the diol monomer and the dicarboxylic acid monomer or theymay be melt blended with the preformed sulfopolyester. A preferredmethod of including colorants is to use a colorant having thermallystable organic colored compounds having reactive groups such that thecolorant is copolymerized and incorporated into the sulfopolyester toimprove its hue. For example, colorants such as dyes possessing reactivehydroxyl and/or carboxyl groups, including, but not limited to, blue andred substituted anthraquinones, may be copolymerized into the polymerchain. When dyes are employed as colorants, they may be added to thecopolyester reaction process after an ester interchange or directesterification reaction.

For the purposes of this invention, the term “fiber” refers to apolymeric body of high aspect ratio capable of being formed into two orthree dimensional articles such as woven or nonwoven fabrics. In thecontext of the present invention, the term “fiber” is synonymous with“fibers” and intented to mean one or more fibers. The fibers of ourinvention may be unicomponent fibers, bicomponent, or multicomponentfibers. The term “unicomponent fiber”, as used herein, is intended tomean a fiber prepared by melt spinning a single sulfopolyester, blendsof one or more sulfopolyesters, or blends of one or more sulfopolyesterswith one or more additional polymers and includes staple, monofilament,and multifilament fibers. “Unicomponent” is intended to be synonymouswith the term “monocomponent” and includes “biconstituent” or“multiconstituent” fibers, and refers to fibers which have been formedfrom at least two polymers extruded from the same extruder as a blend.Unicomponent or biconstituent fibers do not have the various polymercomponents arranged in relatively constantly positioned distinct zonesacross the cross-sectional area of the fiber and the various polymersare usually not continuous along the entire length of the fiber, insteadusually forming fibrils or protofibrils which start and end at random.Thus, the term “unicomponent” is not intended to exclude fibers formedfrom a polymer or blends of one or more polymers to which small amountsof additives may be added for coloration, anti-static properties,lubrication, hydrophilicity, etc. By contrast, the term “multicomponentfiber”, as used herein, intended to mean a fiber prepared by melting thetwo or more fiber forming polymers in separate extruders and bydirecting the resulting multiple polymer flows into one spinneret with aplurality of distribution flow paths but spun together to form onefiber. Multicomponent fibers are also sometimes referred to as conjugateor bicomponent fibers. The polymers are arranged in substantiallyconstantly positioned distinct zones across the cross-section of theconjugate fibers and extend continuously along the length of theconjugate fibers. The configuration of such a multicomponent fiber maybe, for example, a sheath/core arrangement wherein one polymer issurrounded by another or may be a side by side arrangement, a piearrangement or an “islands-in-the-sea” arrangement. For example, amulticomponent fiber may be prepared by extruding the sulfopolyester andone or more water non-dispersible polymers separately through aspinneret having a shaped or engineered tranverse geometry such as, forexample, an “islands-in-the-sea” or segmented pie configuration.Unicomponent fibers, typically, are staple, monofilament ormultifilament fibers that have a shaped or round cross-section. Mostfiber forms are heatset. The fiber may include the various antioxidants,pigments, and additives as described herein.

Monofilament fibers generally range in size from about 15 to about 8000denier per filament (abbreviated herein as “d/f”). Our novel fiberstypically will have d/f values in the range of about 40 to about 5000.Monofilaments may be in the form of unicomponent or multicomponentfibers. The multifilament fibers of our invention will preferably rangein size from about 1.5 micrometers for melt blown webs, about 0.5 toabout 50 d/f for staple fibers, and up to about 5000 d/f formonofilament fibers. Multifilament fibers may also be used as crimped oruncrimped yarns and tows. Fibers used in melt blown web and melt spunfabrics may be produced in microdenier sizes. The term “microdenier”, asused herein, is intended to mean a d/f value of 1 d/f or less. Forexample, the microdenier fibers of the instant invention typically haved/f values of 1 or less, 0.5 or less, or 0.1 or less. Nanofibers canalso be produced by electrostatic spinning.

As noted hereinabove, the sulfopolyesters also are advantageous for thepreparation of bicomponent and multicomponent fibers having a shapedcross section. We have discovered that sulfopolyesters or blends ofsulfopolyesters having a glass transistion temperature (Tg) of at least57° C. are particularly useful for multicomponent fibers to preventblocking and fusing of the fiber during spinning and take up. Thus, ourinvention provides a multicomponent fiber having shaped cross section,comprising:

-   A) a water dispersible sulfopolyester having a glass transistion    temperature (Tg) of at least 57° C., the sulfpolyester comprising:    -   (i) residues of one or more dicarboxylic acids;    -   (ii) about 4 to about 40 mole %, based on the total repeating        units, of residues of at least one sulfomonomer having 2        functional groups and one or more sulfonate groups attached to        an aromatic or cycloaliphatic ring wherein the functional groups        are hydroxyl, carboxyl, or a combination thereof;    -   (iii) one or more diol residues wherein at least 25 mole %,        based on the total diol residues, is a poly(ethylene glycol)        having a structure        H—(OCH₂—CH₂)_(n)—OH        -   wherein n is an integer in the range of 2 to about 500; and    -   (iv) 0 to about 25 mole %, based on the total repeating units,        of residues of a branching monomer having 3 or more functional        groups wherein the functional groups are hydroxyl, carboxyl, or        a combination thereof; and-   B) a plurality of segments comprising one or more    water-nondispersable polymers immiscible with the sulfopolyester,    wherein the segments are substantially isolated from each other by    the sulfopolyester intervening between the segments;    wherein the fiber has an islands-in-the-sea or segmented pie cross    section and contains less than 10 weight percent of a pigment or    filler, based on the total weight of the fiber. The dicarboxylic    acids, diols, sulfopolyester, sulfomonomers, and branching monomers    residues are as described previously for other embodiments of the    invention. For multicomponent fibers, it is advantageous that the    sulfopolyester have a Tg of at least 57° C. Further examples of    glass transition temperatures that may be exhibited by the    sulfopolyester or sulfopolyester blend of our multicomponent fiber    are at least 60° C., at least 65° C., at least 70° C., at least 75°    C., at least 80° C., at least 85° C., and at least 90° C. Further,    to obtain a sulfopolyester with a Tg of at least 57° C., blends of    one or more sulfopolyesters may be used in varying proportions to    obtain a sulfopolyester blend having the desired Tg. The Tg of a    sulfopolyester blend may be calculated by using a weighted average    of the Tg's of the sulfopolyester components. For example,    sulfopolyester having a Tg of 48° C. may be blended in a 25:75 wt:wt    ratio with another sulfopolyester having Tg of 65° C. to give a    sulfopolyester blend having a Tg of approximately 61° C.

The multicomponent fiber comprises a plurality of segments one or morewater-nondispersable polymers immiscible with the sulfopolyester inwhich the segments are substantially isolated from each other by thesulfopolyester intervening between the segments. The term “substantiallyisolated”, as used herein, is intended to mean that the segments are setapart from each other to permit the segments to form individual fibersupon removal of the sulfopolyester. For example, the segments may betouching each others as in, for example, a segmented pie configurationbut can be split apart by impact or when the sulfopolyester is removed.

The ratio by weight of the sulfopolyester to water non-dispersiblepolymer component in the multicomponent fiber of the invention isgenerally in the range of about 60:40 to about 2:98 or, in anotherexample, in the range of about 50:50 to about 5:95. Typically, thesulfopolyester comprises 50% by weight or less of the total weight ofthe mulicomponent fiber.

The segments of multicomponent fiber may comprise one of more waternon-dispersible polymers. Examples of water-nondispersible polymerswhich may be used in segments of the multicomponent fiber include, butare not limited to, polyolefins, polyesters, polyamides, polylactides,polycaprolactone, polycarbonate, polyurethane, and polyvinyl chloride.For example, the water non-dispersible polymer may be polyester such aspoly(ethylene) terephthalate, poly(butylene) terephthalate,poly(cyclohexylene) cyclohexanedicarboxylate, poly(cyclohexylene)terephthalate, poly(trimethylene) terephthalate, and the like. Inanother example, the water-nondispersible polymer biodistintegratable asdetermined by DIN Standard 54900 and/or biodegradable as determined byASTM Standard Method, D6340-98. Examples of biodegradable polyesters andpolyester blends are disclosed in U.S. Pat. Nos. 5,599,858; 5,580,911;5,446,079; and 5,559,171. The term “biodegradable”, as used herein inreference to the water non-dispersible polymers of the presentinvention, is understood to mean that the polymers are degraded underenvironmental influences such as, for example, in a compostingenvironment, in an appropriate and demonstrable time span as defined,for example, by ASTM Standard Method, D6340-98, entitled “Standard TestMethods for Determining Aerobic Biodegradation of Radiolabeled PlasticMaterials in an Aqueous or Compost Environment”. The waternon-dispersible polymers of the present invention also may be“biodisintegratable”, meaning that the polymers are easily fragmented ina composting environment as defined, for example, by DIN Standard 54900.For example, the biodegradable polymer is initially reduced in molecularweight in the environment by the action of heat, water, air, microbesand other factors. This reduction in molecular weight results in a lossof physical properties (tenacity) and often in fiber breakage. Once themolecular weight of the polymer is sufficiently low, the monomers andoligomers are then assimilated by the microbes. In an aerobicenvironment, these monomers or oligomers are ultimately oxidized to CO₂,H₂O, and new cell biomass. In an anaerobic environment, the monomers oroligomers are ultimately converted to CO₂, H₂, acetate, methane, andcell biomass.

For example, water-nondispersible polymer may be an aliphatic-aromaticpolyester, abbreviated herein as “AAPE”. The term “aliphatic-aromaticpolyester”, as used herein, means a polyester comprising a mixture ofresidues from aliphatic or cycloaliphatic dicarboxylic acids or diolsand aromatic dicarboxylic acids or diols. The term “non-aromatic”, asused herein with respect to the dicarboxylic acid and diol monomers ofthe present invention, means that carboxyl or hydroxyl groups of themonomer are not connected through an aromatic nucleus. For example,adipic acid contains no aromatic nucleus in its backbone, i.e., thechain of carbon atoms connecting the carboxylic acid groups, thus is“non-aromatic”. By contrast, the term “aromatic” means the dicarboxylicacid or diol contains an aromatic nucleus in the backbone such as, forexample, terephthalic acid or 2,6-naphthalene dicarboxylic acid.“Non-aromatic”, therefore, is intended to include both aliphatic andcycloaliphatic structures such as, for example, diols and dicarboxylicacids, which contain as a backbone a straight or branched chain orcyclic arrangement of the constituent carbon atoms which may besaturated or paraffinic in nature, unsaturated, i.e., containingnon-aromatic carbon-carbon double bonds, or acetylenic, i.e., containingcarbon-carbon triple bonds. Thus, in the context of the description andthe claims of the present invention, non-aromatic is intended to includelinear and branched, chain structures (referred to herein as“aliphatic”) and cyclic structures (referred to herein as “alicyclic” or“cycloaliphatic”). The term “non-aromatic”, however, is not intended toexclude any aromatic substituents which may be attached to the backboneof an aliphatic or cycloaliphatic diol or dicarboxylic acid. In thepresent invention, the difunctional carboxylic acid typically is aaliphatic dicarboxylic acid such as, for example, adipic acid, or anaromatic dicarboxylic acid such as, for example, terephthalic acid. Thedifunctional hydroxyl compound may be cycloaliphatic diol such as, forexample, 1,4-cyclohexanedimethanol, a linear or branched aliphatic diolsuch as, for example, 1,4-butanediol, or an aromatic diol such as, forexample, hydroquinone.

The AAPE may be a linear or branched random copolyester and/or chainextended copolyester comprising diol residues which comprise theresidues of one or more substituted or unsubstituted, linear orbranched, diols selected from aliphatic diols containing 2 to about 8carbon atoms, polyalkylene ether glycols containing 2 to 8 carbon atoms,and cycloaliphatic diols containing about 4 to about 12 carbon atoms.The substituted diols, typically, will comprise 1 to about 4substituents independently selected from halo, C₆-C₁₀ aryl, and C₁-C₄alkoxy. Examples of diols which may be used include, but are not limitedto, ethylene glycol, diethylene glycol, propylene glycol,1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,3-butanediol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, polyethylene glycol,diethylene glycol, 2,2,4-trimethyl-1,6-hexanediol, thiodiethanol,1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol,2,2,4,4-tetramethyl-1,3-cyclobutanediol, triethylene glycol, andtetraethylene glycol with the preferred diols comprising one or morediols selected from 1,4-butanediol; 1,3-propanediol; ethylene glycol;1,6-hexanediol; diethylene glycol; or 1,4-cyclohexanedimethanol. TheAAPE also comprises diacid residues which contain about 35 to about 99mole %, based on the total moles of diacid residues, of the residues ofone or more substituted or unsubstituted, linear or branched,non-aromatic dicarboxylic acids selected from aliphatic dicarboxylicacids containing 2 to about 12 carbon atoms and cycloaliphatic acidscontaining about 5 to about 10 carbon atoms. The substitutednon-aromatic dicarboxylic acids will typically contain 1 to about 4substituents selected from halo, C₆-C₁₀ aryl, and C₁-C₄ alkoxy.Non-limiting examples of non-aromatic diacids include malonic, succinic,glutaric, adipic, pimelic, azelaic, sebacic, fumaric, 2,2-dimethylglutaric, suberic, 1,3-cyclopentanedicarboxylic,1,4-cyclohexanedicarboxylic, 1,3-cyclohexanedicarboxylic, diglycolic,itaconic, maleic, and 2,5-norbornanedicarboxylic. In addition to thenon-aromatic dicarboxylic acids, the AAPE comprises about 1 to about 65mole %, based on the total moles of diacid residues, of the residues ofone or more substituted or unsubstituted aromatic dicarboxylic acidscontaining 6 to about 10 carbon atoms. In the case where substitutedaromatic dicarboxylic acids are used, they will typically contain 1 toabout 4 substituents selected from halo, C₆-C₁₀ aryl, and C₁-C₄ alkoxy.Non-limiting examples of aromatic dicarboxylic acids which may be usedin the AAPE of our invention are terephthalic acid, isophthalic acid,salts of 5-sulfoisophthalic acid, and 2,6-naphthalenedicarboxylic acid.More preferably, the non-aromatic dicarboxylic acid will comprise adipicacid, the aromatic dicarboxylic acid will comprise terephthalic acid,and the diol will comprise 1,4-butanediol.

Other possible compositions for the AAPE's of our invention are thoseprepared from the following diols and dicarboxylic acids (orpolyester-forming equivalents thereof such as diesters) in the followingmole percentages, based on 100 mole percent of a diacid component and100 mole percent of a diol component:

-   (1) glutaric acid (about 30 to about 75%); terephthalic acid (about    25 to about 70%); 1,4-butanediol (about 90 to 100%); and modifying    diol (0 about 10%);-   (2) succinic acid (about 30 to about 95%); terephthalic acid (about    5 to about 70%); 1,4-butanediol (about 90 to 100%); and modifying    diol (0 to about 10%); and-   (3) adipic acid (about 30 to about 75%); terephthalic acid (about 25    to about 70%); 1,4-butanediol (about 90 to 100%); and modifying diol    (0 to about 10%).

The modifying diol preferably is selected from1,4-cyclohexanedimethanol, triethylene glycol, polyethylene glycol andneopentyl glycol. The most preferred AAPE's are linear, branched orchain extended copolyesters comprising about 50 to about 60 mole percentadipic acid residues, about 40 to about 50 mole percent terephthalicacid residues, and at least 95 mole percent 1,4-butanediol residues.Even more preferably, the adipic acid residues comprise about 55 toabout 60 mole percent, the terephthalic acid residues comprise about 40to about 45 mole percent, and the diol residues comprise about 95 molepercent 1,4-butanediol residues. Such compositions are commerciallyavailable under the trademark EASTAR BIO® copolyester from EastmanChemical Company, Kingsport, Tenn., and under the trademark ECOFLEX®from BASF Corporation.

Additional, specific examples of preferred AAPE's include apoly(tetramethylene glutarate-co-terephthalate) containing (a) 50 molepercent glutaric acid residues, 50 mole percent terephthalic acidresidues, and 100 mole percent 1,4-butanediol residues, (b) 60 molepercent glutaric acid residues, 40 mole percent terephthalic acidresidues, and 100 mole percent 1,4-butanediol residues or (c) 40 molepercent glutaric acid residues, 60 mole percent terephthalic acidresidues, and 100 mole percent 1,4-butanediol residues; apoly(tetramethylene succinate-co-terephthalate) containing (a) 85 molepercent succinic acid residues, 15 mole percent terephthalic acidresidues, and 100 mole percent 1,4-butanediol residues or (b) 70 molepercent succinic acid residues, 30 mole percent terephthalic acidresidues, and 100 mole percent 1,4-butanediol residues; a poly(ethylenesuccinate-co-terephthalate) containing 70 mole percent succinic acidresidues, 30 mole percent terephthalic acid residues, and 100 molepercent ethylene glycol residues; and a poly(tetramethyleneadipate-co-terephthalate) containing (a) 85 mole percent adipic acidresidues, 15 mole percent terephthalic acid residues, and 100 molepercent 1,4-butanediol residues; or (b) 55 mole percent adipic acidresidues, 45 mole percent terephthalic acid residues, and 100 molepercent 1,4-butanediol residues.

The AAPE preferably comprises from about 10 to about 1,000 repeatingunits and preferably, from about 15 to about 600 repeating units. TheAAPE may have an inherent viscosity of about 0.4 to about 2.0 dL/g, ormore preferably about 0.7 to about 1.6 dL/g, as measured at atemperature of 25° C. using a concentration of 0.5 gram copolyester in100 ml of a 60/40 by weight solution of phenol/tetrachloroethane.

The AAPE, optionally, may contain the residues of a branching agent. Themole percentage ranges for the branching agent are from about 0 to about2 mole %, preferably about 0.1 to about 1 mole %, and most preferablyabout 0.1 to about 0.5 mole % based on the total moles of diacid or diolresidues (depending on whether the branching agent contains carboxyl orhydroxyl groups). The branching agent preferably has a weight averagemolecular weight of about 50 to about 5000, more preferably about 92 toabout 3000, and a functionality of about 3 to about 6. The branchingagent, for example, may be the esterified residue of a polyol having 3to 6 hydroxyl groups, a polycarboxylic acid having 3 or 4 carboxylgroups (or ester-forming equivalent groups) or a hydroxy acid having atotal of 3 to 6 hydroxyl and carboxyl groups. In addition, the AAPE maybe branched by the addition of a peroxide during reactive extrusion.

Each segment of the water non-dispersible polymer may be different fromothers in fineness and may be arranged in any shaped or engineeredcross-sectional geometry known to persons skilled in the art. Forexample, the sulfopolyester and a water-nondispersible polymer may beused to prepare a bicomponent fiber having an engineered geometry suchas, for example, a side-by-side, “islands-in-the-sea”, segmented pie,other splitables, sheath/core, or other configurations known to personsskilled in the art. Other multicomponent configurations are alsopossible. Subsequent removal of a side, the “sea”, or a portion of the“pie” can result in very fine fibers. The process of preparingbicomponent fibers also is well known to persons skilled in the art. Ina bicomponent fiber, the sulfopolyester fibers of this invention may bepresent in amounts of about 10 to about 90 weight % and will generallybe used in the sheath portion of sheath/core fibers. The other componentmay be from a wide range of other polymeric materials such as, forexample, poly(ethylene) terephthalate, poly(butylene) terephthalate,poly(trimethylene) terephthalate, polylactides and the like as well aspolyolefins, cellulose esters, and polyamides. Typically, when awater-insoluble or water-nondispersible polymer is used, the resultingbicomponent or multicomponent fiber is not completely water-dispersible.Side by side combinations with significant differences in thermalshrinkage can be utilized for the development of a spiral crimp. Ifcrimping is desired, a saw tooth or stuffer box crimp is generallysuitable for many applications. If the second polymer component is inthe core of a sheath/core configuration, such a core optionally may bestabilized.

The sulfopolyesters are particularly useful for fibers having an“islands-in-the-sea” or “segmented pie” cross section as they onlyrequires neutral or slightly acidic (i.e., “soft” water) to disperse, ascompared to the caustic-containing solutions that are sometimes requiredto remove other water dispersible polymers from multicomponent fibers.Thus another aspect of our invention is is a multicomponent fiber,comprising:

-   -   (A) a water dispersible sulfopolyester having a glass        transistion temperature (Tg) of at least 57° C., the        sulfopolyester comprising:        -   (i) about 50 to about 96 mole % of one or more residues of            isophthalic acid or terephthalic acid, based on the total            acid residues;        -   (ii) about 4 to about 30 mole %, based on the total acid            residues, of a residue of sodiosulfoisophthalic acid;        -   (iii) one or more diol residues wherein at least 25 mole %,            based on the total diol residues, is a poly(ethylene glycol)            having a structure            H—(OCH₂—CH₂)_(n)—OH            -   wherein n is an integer in the range of 2 to about 500;        -   (iv) 0 to about 20 mole %, based on the total repeating            units, of residues of a branching monomer having 3 or more            functional groups wherein the functional groups are            hydroxyl, carboxyl, or a combination thereof; and    -   (B) a plurality of segments comprising one or more        water-nondispersible polymers immiscible with the        sulfopolyester, wherein the segments are substantially isolated        from each other by the sulfopolyester intervening between the        segments;    -   wherein the fiber has an islands-in-the-sea or segmented pie        cross section and contains less than 10 weight percent of a        pigment or filler, based on the total weight of the fiber.        The dicarboxylic acids, diols, sulfopolyester, sulfomonomers,        branching monomers residues, and water non-dispersible polymers        are as described previously. For multicomponent fibers, it is        advantageous that sulfopolyester have a Tg of at least 57° C.        The sulfopolyester may be a single sulfopolyester or a blend of        one or more sulfopolyester polymers. Further examples of glass        transition temperatures that may be exhibited by the        sulfopolyester or sulfopolyester blends are at least 65° C., at        least 70° C., at least 75° C., at least 85° C., and at least        90° C. For example, the sulfopolyester may comprise about 75 to        about 96 mole % of one or more residues of isophthalic acid or        terephthalic acid and about 25 to about 95 mole % of a residue        of diethylene glycol. As described hereinabove, examples of the        water-nondispersible polymers are polyolefins, polyesters,        polyamides, polylactides, polycaprolactone, polycarbonate,        polyurethane, and polyvinyl chloride. In addition, the        water-nondispersible polymer may be biodegradable or        biodisintegratable. For example, the water-nondispersible        polymer may be an aliphatic-aromatic polyester as described        previously.

Our novel multicomponent fiber may be prepared by any number of methodsknown to persons skilled in the art. The present invention thus providesa process for a multicomponent fiber having a shaped cross sectioncomprising: spinning a water dispersible sulfopolyester having a glasstransistion temperature (Tg) of at least 57° C. and one or morewater-nondispersable polymers immiscible with the sulfopolyester into afiber, the sulfopolyester comprising:

-   (i) residues of one or more dicarboxylic acids;-   (ii) about 4 to about 40 mole %, based on the total repeating units,    of residues of at least one sulfomonomer having 2 functional groups    and one or more sulfonate groups attached to an aromatic or    cycloaliphatic ring wherein the functional groups are hydroxyl,    carboxyl, or a combination thereof;-   (iii) one or more diol residues wherein at least 25 mole %, based on    the total diol residues, is a poly(ethylene glycol) having a    structure    H—(OCH₂—CH₂)_(n)—OH    -   wherein n is an integer in the range of 2 to about 500; and-   (iv) 0 to about 25 mole %, based on the total repeating units, of    residues of a branching monomer having 3 or more functional groups    wherein the functional groups are hydroxyl, carboxyl, or a    combination thereof;    wherein the fiber has a plurality of segments comprising the    water-nondispersable polymers and the segments are substantially    isolated from each other by the sulfopolyester intervening between    the segments and the fiber contains less than 10 weight percent of a    pigment or filler, based on the total weight of the fiber. For    example, the multicomponent fiber may be prepared by melting the    sulfopolyester and one or more water non-dispersible polymers in    separate extruders and directing the individual polymer flows into    one spinneret or extrusion die with a plurality of distribution flow    paths such that the water non-dispersible polymer component form    small segments or thin strands which are substantially isolated from    each other by the intervening sulfopolyester. The cross section of    such a fiber may be, for example, a segmented pie arrangement or an    islands-in-the-sea arrangement. In another example, the    sulfopolyester and one or more water non-dispersible polymers are    separately fed to the spinneret orifices and then extruded in    sheath-core form in which the water non-dispersible polymer forms a    “core” that is substantially enclosed by the sulfopolyester “sheath”    polymer. In the case of such concentric fibers, the orifice    supplying the “core” polymer is in the center of the spinning    orifice outlet and flow conditions of core polymer fluid are    strictly controlled to maintain the concentricity of both components    when spinning. Modifications in spinneret orifices enable different    shapes of core and/or sheath to be obtained within the fiber    cross-section. In yet another example, a multicomponent fiber having    a side-by-side cross section or configuration may be produced by    coextruding the water dispersible sulfopolyester and water    non-dispersible polymer through orifices separately and converging    the separate polymer streams at substantially the same speed to    merge side-by-side as a combined stream below the face of the    spinneret; or (2) by feeding the two polymer streams separately    through orifices, which converge at the surface of the spinneret, at    substantially the same speed to merge side-by-side as a combined    stream at the surface of the spinneret. In both cases, the velocity    of each polymer stream, at the point of merge, is determined by its    metering pump speed, the number of orifices, and the size of the    orifice.

The dicarboxylic acids, diols, sulfopolyester, sulfomonomers, branchingmonomers residues, and water non-dispersible polymers are as describedpreviously. The sulfopolyester has a glass transistion temperature of atleast 60° C. Further examples of glass transition temperatures that maybe exhibited by the sulfopolyester or sulfopolyester blend are at least65° C., at least 70° C., at least 75° C., at least 85° C., and at least90° C. In one example, the sulfopolyester may comprise about 50 to about96 mole % of one or more residues of isophthalic acid or terephthalicacid, based on the total acid residues; and about 4 to about 30 mole %,based on the total acid residues, of a residue of sodiosulfoisophthalicacid; and 0 to about 20 mole %, based on the total repeating units, ofresidues of a branching monomer having 3 or more functional groupswherein the functional groups are hydroxyl, carboxyl, or a combinationthereof. In another example, the sulfopolyester may comprise about 75 toabout 96 mole % of one or more residues of isophthalic acid orterephthalic acid and about 25 to about 95 mole % of a residue ofdiethylene glycol. As described hereinabove, examples of thewater-nondispersible polymers are polyolefins, polyesters, polyamides,polylactides, polycaprolactone, polycarbonate, polyurethane, andpolyvinyl chloride. In addition, the water-nondispersible polymer may bebiodegradable or biodisintegratable. For example, thewater-nondispersible polymer may be an aliphatic-aromatic polyester asdescribed previously. Examples of shaped cross sections include, but arenot limited to, islands-in-the-sea, side-by-side, sheath-core, orsegmented pie configurations.

Typically, upon exiting the spinneret, the fibers are quenched with across flow of air whereupon the fibers solidify. Various finishes andsizes may be applied to the fiber at this stage. The cooled fibers,typically, are subsequently drawn and wound up on a take up spool. Otheradditives may be incorporated in the finish in effective amounts likeemulsifiers, antistatics, antimicrobials, antifoams, lubricants,thermostabilizers, UV stabilizers, and the like.

Optionally, the drawn fibers may be textured and wound-up to form abulky continuous filament. This one-step technique is known in the artas spin-draw-texturing. Other embodiments include flat filament(non-textured) yarns, or cut staple fiber, either crimped or uncrimped.

The sulfopolyester may be later removed by dissolving the interfaciallayers or pie segments and leaving the smaller filaments or microdenierfibers of the water non-dispersible polymer(s). Our invention thusprovides a process for microdenier fibers comprising:

-   A. spinning a water dispersible sulfopolyester having a glass    transistion temperature (Tg) of at least 57° C. and one or more    water-nondispersable polymers immiscible with the sulfopolyester    into multicomponent fibers, the sulfopolyester comprising:    -   (i) about 50 to about 96 mole % of one or more residues of        isophthalic acid or terephthalic acid, based on the total acid        residues;    -   (ii) about 4 to about 30 mole %, based on the total acid        residues, of a residue of sodiosulfoisophthalic acid;    -   (iii) one or more diol residues wherein at least 25 mole %,        based on the total diol residues, is a poly(ethylene glycol)        having a structure        H—(OCH₂—CH₂)_(n)—OH        -   wherein n is an integer in the range of 2 to about 500; and    -   (iv) 0 to about 20 mole %, based on the total repeating units,        of residues of a branching monomer having 3 or more functional        groups wherein the functional groups are hydroxyl, carboxyl, or        a combination thereof;    -   wherein the fibers have a plurality of segments comprising the        water-nondispersable polymers wherein the segments are        substantially isolated from each other by the sulfopolyester        intervening between the segments and the fibers contain less        than 10 weight percent of a pigment or filler, based on the        total weight of the fibers; and-   B. contacting the multicomponent fibers with water to remove the    sulfopolyester thereby forming microdenier fibers.    Typically, the multicomponent fiber is contacted with water at a    temperature of about 25° C. to about 100° C., preferably about    50° C. to about 80° C. for a time period of from about 10 to about    600 seconds whereby the sulfopolyester is dissipated or dissolved.    After removal of the sulfopolyester, the remaining microfibers    typically will have an average fineness of 1 d/f or less, typically,    0.5 d/f or less, or more typically, 0.1 d/f or less. Typical    applications of these remaining microfibers include artificial    leathers, suedes, wipes, and filter media. The ionic nature of    sulfopolyesters also results in advantageously poor “solubility” in    saline media, such as body fluids. Such properties are desirable in    personal care products and cleaning wipes that are flushable or    otherwise disposed in sanitary sewage systems. Selected    sulfopolyesters have also been utilized as dispersing agents in dye    baths and soil redeposition preventative agents during laundry    cycles.

The instant invention also includes a fibrous article comprising thewater-dispersible fiber, the multicomponent fiber, or the microdenierfibers described hereinabove. The term “fibrous article” is understoodto mean any article having or resembling fibers. Non-limiting examplesof fibrous articles include multifilament fibers, yarns, cords, tapes,fabrics, melt blown webs, spunbonded webs, thermobonded webs,hydroentangled webs, nonwoven webs and fabrics, and combinationsthereof; items having one or more layers of fibers, such as, forexample, multilayer nonwovens, laminates, and composites from suchfibers, gauzes, bandages, diapers, training pants, tampons, surgicalgowns and masks, feminine napkins; and the like. Further, the fibrousarticles may include replacement inserts for various personal hygieneand cleaning products. The fibrous article of the present invention maybe bonded, laminated, attached to, or used in conjunction with othermaterials which may or may not be water-dispersible. The fibrousarticle, for example, a nonwoven fabric layer, may be bonded to aflexible plastic film or backing of a water-nondispersible material,such as polyethylene. Such an assembly, for example, could be used asone component of a disposable diaper. In addition, the fibrous articlemay result from overblowing fibers onto another substrate to form highlyassorted combinations of engineered melt blown, spunbond, film, ormembrane structures.

The fibrous articles of the instant invention include nonwoven fabricsand webs. A nonwoven fabric is defined as a fabric made directly fromfibrous webs without weaving or knitting operations. For example, themulticomponent fiber of the present invention may be formed into afabric by any known fabric forming process like knitting, weaving,needle punching, and hydroentangling. The resulting fabric or web may beconverted into a microdenier fiber web by exerting sufficient force tocause the multicomponent fibers to split or by contacting the web withwater to remove the sulfopolyester leaving the remaining microdenierfibers behind. Our invention thus provides a process for a microdenierfiber web, comprising:

-   A. spinning a water dispersible sulfopolyester having a glass    transistion temperature (Tg) of at least 57° C. and one or more    water-nondispersable polymers immiscible with the sulfopolyester    into multicomponent fibers, the sulfpolyester comprising:    -   (i) about 50 to about 96 mole % of one or more residues of        isophthalic acid or terephthalic acid, based on the total acid        residues;    -   (ii) about 4 to about 30 mole %, based on the total acid        residues, of a residue of sodiosulfoisophthalic acid;    -   (iii) one or more diol residues wherein at least 25 mole %,        based on the total diol residues, is a poly(ethylene glycol)        having a structure        H—(OCH₂—CH₂)_(n)—OH        -   wherein n is an integer in the range of 2 to about 500; and    -   (iv) 0 to about 20 mole %, based on the total repeating units,        of residues of a branching monomer having 3 or more functional        groups wherein the functional groups are hydroxyl, carboxyl, or        a combination thereof.    -   wherein the multicomponent fibers have a plurality of segments        comprising the water-nondispersable polymers wherein the        segments are substantially isolated from each other by the        sulfopolyester intervening between the segments; and the fiber        contains less than 10 weight percent of a pigment or filler,        based on the total weight of the fiber;-   B. overlapping and collecting the multicomponent fibers of Step A to    form a nonwoven web; and-   C. contacting the nonwoven web with water to remove the    sulfopolyester thereby forming a microdenier fiber web.

The nonwoven assembly is held together by 1) mechanical fiber cohesionand interlocking in a web or mat; 2) various techniques of fusing offibers, including the use of binder fibers, utilizing the thermoplasticproperties of certain polymers and polymer blends; 3) use of a bindingresin such as starch, casein, a cellulose derivative, or a syntheticresin, such as an acrylic latex or urethane; 4) powder adhesive binders;or 5) combinations thereof. The fibers are often deposited in a randommanner, although orientation in one direction is possible, followed bybonding using one of the methods described above.

The fibrous articles of our invention further also may comprise one ormore layers of water-dispersible fibers, multicomponent fibers, ormicrodenier fibers. The fiber layers may be one or more nonwoven fabriclayers, a layer of loosely bound overlapping fibers, or a combinationthereof. In addition, the fibrous articles may include personal andhealth care products such as, but not limited to, child care products,such as infant diapers; child training pants; adult care products, suchas adult diapers and adult incontinence pads; feminine care products,such as feminine napkins, panty liners, and tampons; wipes;fiber-containing cleaning products; medical and surgical care products,such as medical wipes, tissues, gauzes, examination bed coverings,surgical masks, gowns, bandages, and wound dressings; fabrics;elastomeric yarns, wipes, tapes, other protective barriers, andpackaging material. The fibrous articles may be used to absorb liquidsor may be pre-moistened with various liquid compositions and used todeliver these compositions to a surface. Non-limiting examples of liquidcompositions include detergents; wetting agents; cleaning agents; skincare products, such as cosmetics, ointments, medications, emollients,and fragrances. The fibrous articles also may include various powdersand particulates to improve absorbency or as delivery vehicles. Examplesof powders and particulates include, but are not limited to, talc,starches, various water absorbent, water-dispersible, or water swellablepolymers, such as super absorbent polymers, sulfopolyesters, andpoly(vinylalcohols), silica, pigments, and microcapsules. Additives mayalso be present, but are not required, as needed for specificapplications. Examples of additives include, but are not limited to,oxidative stabilizers, UV absorbers, colorants, pigments, opacifiers(delustrants), optical brighteners, fillers, nucleating agents,plasticizers, viscosity modifiers, surface modifiers, antimicrobials,disinfectants, cold flow inhibitors, branching agents, and catalysts.

In addition to being water-dispersible, the fibrous articles describedabove may be flushable. The term “flushable” as used herein meanscapable of being flushed in a conventional toilet, and being introducedinto a municipal sewage or residential septic system, without causing anobstruction or blockage in the toilet or sewage system.

The fibrous article may further comprise a water-dispersible filmcomprising a second water-dispersible polymer. The secondwater-dispersible polymer may be the same as or different from thepreviously described water-dispersible polymers used in the fibers andfibrous articles of the present invention. In one embodiment, forexample, the second water-dispersible polymer may be an additionalsulfopolyester which, in turn, comprises: (i) about 50 to about 96 mole% of one or more residues of isophthalic acid or terephthalic acid,based on the total acid residues; (ii) about 4 to about 30 mole %, basedon the total acid residues, of a residue of sodiosulfoisophthalic acid;(iii) one or more diol residues wherein at least 15 mole %, based on thetotal diol residues, is a poly(ethylene glycol) having a structureH—(OCH₂—CH₂)_(n)—OHwherein n is an integer in the range of 2 to about 500; (iv) 0 to about20 mole %, based on the total repeating units, of residues of abranching monomer having 3 or more functional groups wherein thefunctional groups are hydroxyl, carboxyl, or a combination thereof. Theadditional sulfopolyester may be blended with one or more supplementalpolymers, as described hereinabove, to modify the properties of theresulting fibrous article. The supplemental polymer may or may not bewater-dispersible depending on the application. The supplemental polymermay be miscible or immiscible with the additional sulfopolyester.

The additional sulfopolyester may contain other concentrations ofisophthalic acid residues, for example, about 60 to about 95 mole %, andabout 75 to about 95 mole %. Further examples of isophthalic acidresidue concentrations ranges are about 70 to about 85 mole %, about 85to about 95 mole % and about 90 to about 95 mole %. The additionalsulfopolyester also may comprise about 25 to about 95 mole % of theresidues of diethylene glycol. Further examples of diethylene glycolresidue concentration ranges include about 50 to about 95 mole %, about70 to about 95 mole %, and about 75 to about 95 mole %. The additionalsulfopolyester also may include the residues of ethylene glycol and/or1,4-cyclohexanedimethanol. Typical concentration ranges of CHDM residuesare about 10 to about 75 mole %, about 25 to about 65 mole %, and about40 to about 60 mole %. Typical concentration ranges of ethylene glycolresidues are are about 10 to about 75 mole %, about 25 to about 65 mole%, and about 40 to about 60 mole %. In another embodiment, theadditional sulfopolyester comprises is about 75 to about 96 mole % ofthe residues of isophthalic acid and about 25 to about 95 mole % of theresidues of diethylene glycol.

According to the invention, the sulfopolyester film component of thefibrous article may be produced as a monolayer or multilayer film. Themonolayer film may be produced by conventional casting techniques. Themultilayered films may be produced by conventional lamination methods orthe like. The film may be of any convenient thickness, but totalthickness will normally be between about 2 and about 50 mil.

The film-containing fibrous articles may include one or more layers ofwater-dispersible fibers as described above. The fiber layers may be oneor more nonwoven fabric layers, a layer of loosely bound overlappingfibers, or a combination thereof. In addition, the film-containingfibrous articles may include personal and health care products asdescribed hereinabove.

As described previously, the fibrous articles also may include variouspowders and particulates to improve absorbency or as delivery vehicles.Thus, in one embodiment, our fibrous article comprises a powdercomprising a third water-dispersible polymer that may be the same as ordifferent from the water-dispersible polymer components describedpreviously herein. Other examples of powders and particulates include,but are not limited to, talc, starches, various water absorbent,water-dispersible, or water swellable polymers, such aspoly(acrylonitiles), sulfopolyesters, and poly(vinyl alcohols), silica,pigments, and microcapsules.

Our novel fiber and fibrous articles have many possible uses in additionto the applications described above. One novel application involves themelt blowing a film or nonwoven fabric onto flat, curved, or shapedsurfaces to provide a protective layer. One such layer might providesurface protection to durable equipment during shipping. At thedestination, before putting the equipment into service, the outer layersof sulfopolyester could be washed off. A further embodiment of thisgeneral application concept could involve articles of personalprotection to provide temporary barrier layers for some reusable orlimited use garments or coverings. For the military, activated carbonand chemical absorbers could be sprayed onto the attenuating filamentpattern just prior to the collector to allow the melt blown matrix toanchor these entities on the exposed surface. The chemical absorbers caneven be changed in the forward operations area as the threat evolves bymelt blowing on another layer.

A major advantage inherent to sulfopolyesters is the facile ability toremove or recover the polymer from aqueous dispersions via flocculationor precipitation by adding ionic moieties (i.e., salts). Other methods,such as pH adjustment, adding nonsolvents, freezing, and so forth mayalso be employed. Therefore, fibrous articles, such as outer wearprotective garments, after successful protective barrier use and even ifthe polymer is rendered as hazardous waste, can potentially be handledsafely at much lower volumes for disposal using accepted protocols, suchas incineration.

Undissolved or dried sulfopolyesters are known to form strong adhesivebonds to a wide array of substrates, including, but not limited to fluffpulp, cotton, acrylics, rayon, lyocell, PLA (polylactides), celluloseacetate, cellulose acetate propionate, poly(ethylene) terephthalate,poly(butylene) terephthalate, poly(trimethylene) terephthalate,poly(cyclohexylene) terephthalate, copolyesters, polyamides (nylons),stainless steel, aluminum, treated polyolefins, PAN(polyacrylonitriles), and polycarbonates. Thus, our nonwoven fabrics maybe used as laminating adhesives or binders that may be bonded by knowntechniques, such as thermal, radio frequency (RF), microwave, andultrasonic methods. Adaptation of sulfopolyesters to enable RFactivation is disclosed in a number of recent patents. Thus, our novelnonwoven fabrics may have dual or even multifunctionality in addition toadhesive properties. For example, a disposable baby diaper could beobtained where a nonwoven of the present invention serves as both anwater-responsive adhesive as well as a fluid managing component of thefinal assembly.

Our invention also provides a process for water-dispersible fiberscomprising (I) heating a water-dispersible polymer composition to atemperature above its flow point, wherein the polymer compositioncomprises (i) residues of one or more dicarboxylic acids; (ii) about 4to about 40 mole %, based on the total repeating units, of residues ofat least one sulfomonomer having 2 functional groups and one or moremetal sulfonate groups attached to an aromatic or cycloaliphatic ringwherein the functional groups are hydroxyl, carboxyl, or a combinationthereof; and (iii) one or more diol residues wherein at least 20 mole %,based on the total diol residues, is a poly(ethylene glycol) having astructureH—(OCH₂—CH₂)_(n)—OHwherein n is an integer in the range of 2 to about 500; (iv) 0 to about25 mole %, based on the total repeating units, of residues of abranching monomer having 3 or more functional groups wherein thefunctional groups are hydroxyl, carboxyl, or a combination thereof;wherein the polymer composition contains less than 10 weight percent ofa pigment or filler, based on the total weight of the polymercomposition; and (II) melt spinning filaments. As described hereinabove,a water-dispersible polymer, optionally, may be blended with thesulfopolyester. In addition, a water-nondispersible polymer, optionally,may be blended with the sulfopolyester to form a blend such that blendis an immiscible blend. The term “flow point”, as used herein, means thetemperature at which the viscosity of the polymer composition permitsextrusion or other forms of processing through a spinneret or extrusiondie. The dicarboxylic acid residue may comprise from about 60 to about100 mole % of the acid residues depending on the type and concentrationof the sulfomonomer. Other examples of concentration ranges ofdicarboxylic acid residues are from about 60 mole % to about 95 mole %and about 70 mole % to about 95 mole %. The preferred dicarboxylic acidresidues are isophthalic, terephthalic, and 1,4-cyclohexanedicarboxylicacids or if diesters are used, dimethyl terephthalate, dimethylisophthalate, and dimethyl-1,4-cyclohexanedicarboxylate with theresidues of isophthalic and terephthalic acid being especiallypreferred.

The sulfomonomer may be a dicarboxylic acid or ester thereof containinga sulfonate group, a diol containing a sulfonate group, or a hydroxyacid containing a sulfonate group. Additional examples of concentrationranges for the sulfomonomer residues are about 4 to about 25 mole %,about 4 to about 20 mole %, about 4 to about 15 mole %, and about 4 toabout 10 mole %, based on the total repeating units. The cation of thesulfonate salt may be a metal ion such as Li⁺, Na⁺, K⁺, Mg⁺⁺, Ca⁺⁺,Ni⁺⁺, Fe⁺⁺, and the like. Alternatively, the cation of the sulfonatesalt may be non-metallic such as a nitrogenous base as describedpreviously. Examples examples of sulfomonomer residues which may be usedin the process of the present invention are the metal sulfonate salt ofsulfophthalic acid, sulfoterephthalic acid, sulfoisophthalic acid, orcombinations thereof. Another example of sulfomonomer which may be usedis 5-sodiosulfoisophthalic acid or esters thereof. If the sulfomonomerresidue is from 5-sodiosulfoisophthalic acid, typical sulfomonomerconcentration ranges are about 4 to about 35 mole %, about 8 to about 30mole %, and about 10 to 25 mole %, based on the total acid residues.

The sulfopolyester of our includes one or more diol residues which mayinclude aliphatic, cycloaliphatic, and aralkyl glycols. Thecycloaliphatic diols, for example, 1,3- and 1,4-cyclohexanedimethanol,may be present as their pure cis or trans isomers or as a mixture of cisand trans isomers. Non-limiting examples of lower molecular weightpolyethylene glycols, e.g., wherein n is from 2 to 6, are diethyleneglycol, triethylene glycol, and tetraethylene glycol. Of these lowermolecular weight glycols, diethylene and triethylene glycol are mostpreferred. The sulfopolyester may optionally include a branchingmonomer. Examples of branching monomers are as described hereinabove.Further examples of branching monomer concentration ranges are from 0 toabout 20 mole % and from 0 to about 10 mole %. The sulfpolyester of ournovel process has a Tg of at least 25° C. Further examples of glasstransition temperatures exhibited by the sulfopolyester are at least 30°C., at least 35° C., at least 40° C., at least 50° C., at least 60° C.,at least 65° C., at least 80° C., and at least 90° C. Although otherTg's are possible, typical glass transition temperatures of the drysulfopolyesters our invention are about 30° C., about 48° C., about 55°C., about 65° C., about 70° C., about 75° C., about 85° C., and about90° C.

The water-dispersible fibers are prepared by a melt blowing process. Thepolymer is melted in an extruder and forced through a die. The extrudateexiting the die is rapidly attenuated to ultrafine diameters by hot,high velocity air. The orientation, rate of cooling, glass transitiontemperature (T_(g)), and rate of crystallization of the fiber areimportant because they affect the viscosity and processing properties ofthe polymer during attenuation. The filament is collected on a renewablesurface, such as a moving belt, cylindrical drum, rotating mandrel, andso forth. Predrying of pellets (if needed), extruder zone temperature,melt temperature, screw design, throughput rate, air temperature, airflow (velocity), die air gap and set back, nose tip hole size, dietemperature, die-to-collector (DCP) distance, quenching environment,collector speed, and post treatments are all factors that influenceproduct characteristics such as filament diameters, basis weight, webthickness, pore size, softness, and shrinkage. The high velocity airalso may be used to move the filaments in a somewhat random fashion thatresults in extensive interlacing. If a moving belt is passed under thedie, a nonwoven fabric can be produced by a combination of over-lappinglaydown, mechanical cohesiveness, and thermal bonding of the filaments.Overblowing onto another substrate, such as a spunbond or backing layer,is also possible. If the filaments are taken up on an rotating mandrel,a cylindrical product is formed. A water-dispersible fiber lay-down canalso be prepared by the spunbond process.

The instant invention, therefore, further provides a process forwater-dispersible, nonwoven fabric comprising (A) heating awater-dispersible polymer composition to a temperature above its flowpoint, wherein the polymer composition comprises: (i) residues of one ormore dicarboxylic acids; (ii) about 4 to about 40 mole %, based on thetotal repeating units, of residues of at least one sulfomonomer having 2functional groups and one or more metal sulfonate groups attached to anaromatic or cycloaliphatic ring wherein the functional groups arehydroxyl, carboxyl, or a combination thereof; (iii) one or more diolresidues wherein at least 20 mole %, based on the total diol residues,is a poly(ethylene glycol) having a structureH—(OCH₂—CH₂)_(n)—OHwherein n is an integer in the range of 2 to about 500; (iv) 0 to about25 mole %, based on the total repeating units, of residues of abranching monomer having 3 or more functional groups wherein thefunctional groups are hydroxyl, carboxyl, or a combination thereof;wherein the sulfopolyester has a glass transistion temperature (Tg) ofat least 25° C.; wherein the polymer composition contains less than 10weight percent of a pigment or filler, based on the total weight of thepolymer composition; (B) melt-spinning filaments; and (C) overlappingand collecting the filaments of Step B to form a nonwoven fabric. Asdescribed hereinabove, a water-dispersible polymer, optionally, may beblended with the sulfopolyester. In addition, a water-nondispersiblepolymer, optionally, may be blended with the sulfopolyester to form ablend such that blend is an immiscible blend. The dicarboxylic acid,sulfomonomer, and branching monomer residues are as describedpreviously. The sulfpolyester has a Tg of at least 25° C. Furtherexamples of glass transition temperatures exhibited by thesulfopolyester are at least 30° C., at least 35° C., at least 40° C., atleast 50° C., at least 60° C., at least 65° C., at least 80° C., and atleast 90° C. Although other Tg's are possible, typical glass transitiontemperatures of the dry sulfopolyesters our invention are about 30° C.,about 48° C., about 55° C., about 65° C., about 70° C., about 75° C.,about 85° C., and about 90° C. The invention is further illustrated bythe following examples.

EXAMPLES

All pellet samples were predried under vacuum at room temperature for atleast 12 hours. The dispersion times shown in Table 3 are for eithercomplete dispersion or dissolution of the nonwoven fabric samples. Theabbreviation “CE”, used in Tables 2 and 3 mean “comparative example”.

Example 1

A sulfopolyester containing 76 mole %, isophthalic acid, 24 mole % ofsodiosulfoisophthalic acid, 76 mole % diethylene glycol, and 24 mole %1,4-cyclohexanedimethanol with an Ih.V. of 0.29 and a Tg of 48° C. wasmeltblown through a nominal 6-inch die (30 holes/inch in the nosepiece)onto a cylindrical collector using the conditions shown in Table 1.Interleafing paper was not required. A soft, handleable, flexible webwas obtained that did not block during the roll winding operation.Physical properties are provided in Table 2. A small piece (1″×3″) ofthe nonwoven fabric was easily dispersed in both room temperature (RT)and 50° C. water with slight agitation as shown by data in Table 3.

TABLE 1 Melt Blowing Conditions Operating Condition Typical Value DieConfiguration Die tip hole diameter 0.0185 inches Number of holes 120Air gap 0.060 inches Set back 0.060 inches Extruder Barrel Temperatures(° F.) Zone 1 350 Zone 2 510 Zone 3 510 Die Temperatures (° F.) Zone 4510 Zone 5 510 Zone 6 510 Zone 7 510 Zone 8 510 Air Temperatures (° F.)Furnace exit 1 350 Furnace exit 2 700 Furnace exit 3 700 Die 530-546Extrusion Conditions Air pressure 3.0 psi Melt pressure after pump99-113 psi Take Up Conditions Throughput 0.3 g/hole/min 0.5 g/hole/minBasis weight 36 g/m² Collector speed 20 ft/min Collector distance 12inches

TABLE 2 Physical Properties of Nonwovens Tg/Tm (° C.) Ex- FilamentDiameter (μm) IhV (sulfopoly./ ample Minimum Maximum Average(before/after) PP) 1 5 18 8.7 0.29/0.26 39/not applicable 2 3 11 7.70.40/0.34 36/not applicable CE 1 2 20 8 Not measured 36/163 CE 2 4 10 7Not measured 36/164 CE 3 4 11 6 Not measured 35/161

TABLE 3 Dispersbility of Nonwovens Initial Water Disinte- SignificantComplete Ex- Temperature gration Disintegration Dispersion ample (° C.)(minutes) (minutes) (minutes) 1 23 <0.25 1 2 50 <0.17 0.5 1 2 23 8 1419  50 <0.5 5 8 80 <0.5 2 5 CE 1 23 0.5 >15 No dispersion of PP 500.5 >15 No dispersion of PP CE 2 23 0.5 >15 No dispersion of PP 500.5 >15 No dispersion of PP CE 3 23 <0.5 6 No dispersion of PP 50 <0.5 4No dispersion of PP

Example 2

A sulfopolyester containing 89 mole %, isophthalic acid, 11 mole % ofsodiosulfoisophthalic acid, 72 mole % diethylene glycol, and 28 mole %ethylene glycol with an Ih.V. of 0.4 and a Tg of 35° C. was meltblownthrough a 6-inch die using conditions similar to Table 1. A soft,handleable, flexible web was obtained that did not block during a rollwinding operation. Physical properties are provided in Table 2. A smallpiece (1″×2″) of the nonwoven fabric was easily and completely dispersedat 50° C. and 80° C.; at RT (23° C.), the fabric required a longerperiod of time for complete dispersion as shown by the data in Table 3.

It was found that the compositions in Examples 1 and 2 can be overblownonto other nonwoven substrates. It is also possible to condense and wrapshaped or contoured forms that are used instead of conventional webcollectors. Thus, it is possible to obtain circular “roving” or plugforms of the webs.

Comparative Examples 1-3

Pellets of a sulfopolyester containing 89 mole %, isophthalic acid, 11mole % of sodiosulfoisophthalic acid, 72 mole % diethylene glycol, and28 mole % ethylene glycol with an Ih.V. of 0.4 and a Tg of 35° C. werecombined with polypropylene (Basell PF 008) pellets in bicomponentratios (by wt %) of:

-   -   75 PP: 25 sulfopolyester (Example 3)    -   50 PP: 50 sulfopolyester (Example 4)    -   25 PP: 75 sulfopolyester (Example 5)

The PP had a MFR (melt flow rate) of 800. A melt blowing operation wasperformed on a line equipped with a 24-inch wide die to yieldhandleable, soft, flexible, but nonblocking webs with the physicalproperties provided in Table 2. Small pieces (1″×4″) of nonwoven fabricreadily disintegrated as reported in Table 3. None of the fibers,however, were completely water-dispersible because of the insolublepolypropylene component.

Example 3

A circular piece (4″ diameter) of the nonwoven produced in Example 2 wasused as an adhesive layer between two sheets of cotton fabric. AHannifin melt press was used to fuse the two sheets of cotton togetherby applying a pressure 35 psig at 200° C. for 30 seconds. The resultantassembly exhibited exceptionally strong bond strength. The cottonsubstrate shredded before adhesive or bond failure. Similar results havealso been obtained with other cellulosics and with PET polyestersubstrates. Strong bonds were also produced by ultrasonic bondingtechniques.

Comparative Example 4

A PP (Exxon 3356G) with a 1200 MFR was melt blown using a 24″ die toyield a flexible nonwoven fabric that did not block and was easilyunwound from a roll. Small pieces (1″×4″) did not show any response(i.e., no disintegration or loss in basis weight) to water when immersedin water at RT or 50° C. for 15 minutes.

Example 4

Unicomponent fibers of a sulfopolyester containing 82 mole % isophthalicacid, 18 mole % of sodiosulfoisophthalic acid, 54 mole % diethyleneglycol, and 46 mole % 1,4-cyclohexanedimethanol with a Tg of 55° C. weremelt spun at melt temperatures of 245° C. (473° F.) on a lab staplespinning line. As-spun denier was approximately 8 d/f. Some blocking wasencountered on the take-up tubes, but the 10-filament strand readilydissolved within 10-19 seconds in unagitated, demineralized water at 82°C. and a pH between 5 and 6.

Example 5

Unicomponent fibers obtained from a blend (75:25) of a sulfopolyestercontaining 82 mole % isophthalic acid, 18 mole % ofsodiosulfoisophthalic acid, 54 mole % diethylene glycol, and 46 mole %1,4-cyclohexanedimethanol (Tg of 55° C.) and a sulfopolyester containing91 mole % isophthalic acid, 9 mole % of sodiosulfoisophthalic acid, 25mole % diethylene glycol, and 75 mole % 1,4-cyclohexanedimethanol (Tg of65° C.), respectively, were melt spun on a lab staple spinning line. Theblend has a Tg of 57° C. as calculated by taking a weighted average ofthe Tg's of the component sulfopolyesters. The 10-filament strands didnot show any blocking on the take-up tubes, but readily dissolved within20-43 seconds in unagitated, demineralized water at 82° C. and a pHbetween 5 and 6.

Example 6

The blend described in Example 5 was co-spun with PET to yieldbicomponent islands-in-the-sea fibers. A configuration was obtainedwhere the sulfopolyester “sea” is 20 wt % of the fiber containing 80 wt% of PET “islands”. The spun yarn elongation was 190% immediately afterspinning. Blocking was not encountered as the yarn was satisfactorilyunwound from the bobbins and processed a week after spinning. In asubsequent operation, the “sea” was dissolved by passing the yarnthrough an 88° C. soft water bath leaving only fine PET filaments.

Example 7

This prophetic example illustrates the possible application of themulticomponent and microdenier fibers of the present invention to thepreparation of specialty papers. The blend described in Example 5 isco-spun with PET to yield bicomponent islands-in-the-sea fibers. Thefiber contains approximately 35 wt % sulfopolyester “sea” component andapproximately 65 wt % of PET “islands”. The uncrimped fiber is cut to ⅛inch lengths. In simulated papermaking, these short-cut bicomponentfibers are added to the refining operation. The sulfopolyester “sea” isremoved in the agitated, aqueous slurry thereby releasing themicrodenier PET fibers into the mix. At comparable weights, themicrodenier PET fibers (“islands”) are more effective to increase papertensile strength than the addition of coarse PET fibers.

1. A fiber comprising: (A) a sulfopolyester having a glass transistiontemperature (Tg) of at least 25° C., said sulfopolyester comprising: (i)residues of one or more dicarboxylic acids; (ii) about 4 to about 40mole %, based on the total repeating units, of residues of at least onesulfomonomer having 2 functional groups and one or more sulfonate groupsattached to an aromatic or cycloaliphatic ring wherein said functionalgroups are hydroxyl, carboxyl, or a combination thereof; (iii) one ormore diol residues wherein at least 25 mole %, based on the total diolresidues, is a poly(ethylene glycol) having a structureH—(OCH₂—CH₂)_(n)—OH wherein n is an integer in the range of 2 to about500; and (iv) 0 to about 25 mole %, based on the total repeating units,of residues of a branching monomer having 3 or more functional groupswherein said functional groups are hydroxyl, carboxyl, or a combinationthereof; (B) optionally, a water-dispersible polymer blended with saidsulfopolyester; and (C) optionally, a water-nondispersible polymerblended with said sulfopolyester with the proviso that said blend is animmiscible blend; wherein said fiber is water dispersible and containsless than 8 weight percent of a pigment or filler, based on the totalweight of said fiber.
 2. The fiber according to claim 1 in which saiddicarboxylic acids are selected from aliphatic diacids, cycloaliphaticdicarboxylic acids, aromatic dicarboxylic acids, and combinationsthereof.
 3. The fiber according to claim 2 in which said dicarboxylicacids are selected from succinic, glutaric, adipic, azelaic, sebacic,fumaric, maleic, itaconic, 1,3-cyclohexane dicarboxylic,1,4-cyclohexanedicarboxylic, diglycolic, 2,5-norbornanedicarboxylic,phthalic, terephthallc, 1,4-naphthalenedlcarboxylic,2,5-naphthalenedicarboxylic, 2,6-naphthalenedicarboxylic,2,7-naphthalenedicarboxylic, diphenic, 4,4′-oxydibenzoic,4,4′-sulfonyldibenzoic, isophthalic, and combinations thereof.
 4. Thefiber according to claim 3 in which said sulfomonomer is a metalsulfonate salt of a sulfophthalic acid, sulfoterephthalic acid,sulfoisophthalic acid, or combinations thereof.
 5. The fiber accordingto claim 4 in which said diol residues are selected from ethyleneglycol, diethylene glycol, triethylene glycol, poly(ethylene) glycols,1,3-propanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol,2,2-dimethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol,2-ethyl-2-isobutyl-1,3-propanediol, 1,3-butanedlol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,6-hexanediol,thiodiethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol,1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol,p-xylylenediol, and combinations thereof.
 6. The fiber according toclaim 5 in which said branching monomer is 1,1,1-trimethylol propane,1,1,1-trimethylolethane, glycerin, pentaerythritol, erythritol,threitol, dipentaerythritol, sorbitol, trimellitic anhydride,pyromellitic dianhydride, dimethylol propionic acid, or combinationsthereof.
 7. A fiber comprising: (A) a sulfopolyester having a glasstransistion temperature (Tg) of at least 25° C., said sulfopolyestercomprising: (i) about 50 to about 96 mole % of one or more residues ofisophthalic acid or terephthalic acid, based on the total acid residues;(ii) about 4 to about 30 mole %, based on the total acid residues, of aresidue of sodiosulfoisophthalic acid; (iii) one or more diol residueswherein at least 25 mole %, based on the total diol residues, is apoly(ethylene glycol) having a structureH—(OCH₂—CH₂)_(n)—OH wherein n is an integer in the range of 2 to about500; (iv) 0 to about 20 mole %, based on the total repeating units, ofresidues of a branching monomer having 3 or more functional groupswherein said functional groups are hydroxyl, carboxyl, or a combinationthereof: (B) optionally, a first water-dispersible polymer blended withsaid sulfopolyester; and (C) optionally, a water-nondispersibie polymerblended with said sulfopolyester to form a blend with the proviso thatsaid blend is an immiscible blend; wherein said fiber iswater-dispersible and contains less than 8 weight percent of a pigmentor filler, based on the total weight of said fiber.
 8. The fiberaccording to claim 7 comprising a first water-dispersible polymerblended with said sulfopolyester.
 9. The fiber according to claim 7comprising a water-nondispersible polymer blended to form a blend inwhich said blend is an immiscible blend.
 10. The fiber according toclaim 7 in which said sulfopolyester comprises about 75 to about 96 mole% of one or more residues of isophthalic acid or terephthalic acid,based on the total acid residues and about 25 to about 95 mole % ofresidues of diethylene glycol, based on the total diol residues.
 11. Thefiber according to claim 10 in which said fiber is a staple,monofilament, or a multifilament fiber and has a shaped cross-section.12. A fibrous article comprising the fiber of claim
 11. 13. The fibrousarticle according to claim 12 in which said article is selected from ayarn, fabric, melt blown web, spunbonded web, nonwoven fabric, andcombinations thereof.
 14. The fibrous article according to claim 12 inwhich said article comprises one or more layers of fibers.
 15. Thefibrous article according to claim 14 in which said article is a wipe,gauze, tissue, diaper, fiber-containing cleaning product, laminatingbinder, sanitary napkin, panty liner, tampon, training pants,incontinent product, bandage, or surgical dressing.
 16. The fibrousarticle according to claim 15 in which said article is flushable. 17.The fibrous article according to claim 12 further comprising awater-dispersible film in which said water-dispersible film comprises asecond water-dispersible polymer.
 18. The fibrous article according toclaim 17 in which said second water-dispersible polymer comprises anadditional sulfopolyester, said additional sulfopolyester comprising:(i) about 50 to about 96 mole % of one or more residues of isophthalicacid or terephthalic acid, based on the total acid residues; (ii) about4 to about 30 mole %, based on the total acid residues, of a residue ofsodiosulfoisophthalic acid; (iii) one or more diol residues wherein atleast 15 mole %, based on the total diol residues, is a poly(ethyleneglycol) having a structureH—(OCH₂—CH₂)_(n)—OH wherein n is an integer in the range of 2 to about500; and (iv) 0 to about 20 mole %, based on the total repeating units,of residues of a branching monomer having 3 or more functional groupswherein said functional groups are hydroxyl, carboxyl, or a combinationthereof.
 19. The fibrous article according to claim 18 in which saidadditional sulfopolyester comprises about 75 to about 96 mole % of oneor more residues of isophthalic acid or terephthalic acid, based on thetotal acid residues, and about 25 to about 95 mole % of residues ofdiethylene glycol, based on the total diol residues.
 20. The fibrousarticle according to claim 18 further comprising a powder in which saidpowder comprises a third water-dispersible polymer.
 21. The fibrousarticle according to claim 18 in which said article is a wipe, gauze,tissue, diaper, fiber-containing cleaning product, sanitary napkin,panty liner, tampon, training pants, incontinent product, bandage, orsurgical dressing.
 22. The fibrous article according to claim 21 inwhich said article is flushable.
 23. The fiber according to claim 1which contains less than 5 weight percent of a pigment or filler, basedon the total weight of said fiber.
 24. The fiber according to claim 7which contains less than 5 weight percent of a pigment or filler, basedon the total weight of said fiber.
 25. A fibrous article comprising thefiber of claim
 24. 26. A fiber comprising: (A) a sulfopolyester having aglass transistion temperature (Tg) of at least 25° C., saidsulfopolyester comprising: (i) residues of one or more dicarboxylicacids; (ii) about 4 to about 40 mole %, based on the total repeatingunits, of residues of at least one sulfomonomer having 2 functionalgroups and one or more sulfonate groups attached to an aromatic orcycloaliphatic ring wherein said functional groups are hydroxyl,carboxyl, or a combination thereof; (iii) one or more diol residueswherein at least 25 mole %, based on the total diol residues, is apoly(ethylene glycol) having a structureH—(OCH₂—CH₂ )_(n)—OH wherein n is an integer in the range of 2 to about500; and (iv) 0 to about 25 mole %, based on the total repeating units,of residues of a branching monomer having 3 or more functional groupswherein said functional groups are hydroxyl, carboxyl, or a combinationthereof; (B) optionally, a water-dispersible polymer blended with saidsulfopolyester; and (C) optionally, a water-nondispersible polymerblended with said sulfopolyester with the proviso that said blend is animmiscible blend; wherein said fiber is water dispersible and containsno wax.
 27. A fibrous article comprising the fiber of claim 26.